Introduction to Computer Security
Date: Nov 15, 2019
In this sample chapter from Computer Security Fundamentals, 4th Edition, you will learn how to identify the top threats to a network: security breaches, denial of service attacks, and malware.
Introduction
Since the first edition of this book, the prevalence of online transactions has increased dramatically. In 2004 we had e-commerce via websites; in 2019 we have smart phone apps, the Internet of Things, medical devices that communicate wirelessly, as well as an expanded use of e-commerce websites. We also have Wi-Fi–enabled cars and smart homes. Internet traffic is far more than just humorous YouTube videos or Facebook updates about our vacations. Now it is the heart and soul of commerce, both domestic and international. Internet communication even plays a central role in military operations and diplomatic relations. In addition to smart phones, we now have smart watches and even vehicles that have Wi-Fi hotspots and smart technology. Our lives are inextricably intertwined with the online world. We file our taxes online, shop for homes online, book vacations online, and even look for dates online.
Because so much of our business is transacted online, a great deal of personal information is stored in computers. Medical records, tax records, school records, and more are all stored in computer databases. Personal information is often called personally identifiable information (PII), and health-related data is usually termed personal health information (PHI). This leads to some very important questions:
How is information safeguarded?
What are the vulnerabilities to these systems?
What steps are taken to ensure that these systems and data are safe?
Who can access my information?
Unfortunately, not only have technology and Internet access expanded since the original publication of this book, but so have the dangers. How serious is the problem? According to a 2018 article from the Center for Strategic and International Studies, cybercrime has reached over $600 billion a year in damages and is likely to exceed $1 trillion per year soon. Cybercrime is now an economic and strategic problem that even affects national security.”1
Forbes magazine reported that there were 2,216 data breaches and more than 53,000 incidents in the 12 months ending March 2018.2 The specific number may vary from one study to the next, but the primary point remains the same: Cybercrime is increasing. This is due, in part, to the increasing number of connected devices. Every connected device is yet another potential target. There is also easy access to cybercrime tools and weapons on the Internet. All of these factors increase the opportunity for cybercrime.
In spite of daily horror stories, however, many people (including some law enforcement professionals and trained computer professionals) lack an adequate understanding about the reality of these threats. Clearly the media will focus attention on the most dramatic computer security breaches, not necessarily giving an accurate picture of the most plausible threat scenarios. It is not uncommon to encounter the occasional system administrator whose knowledge of computer security is inadequate.
This chapter outlines current dangers, describes the most common types of attacks on your personal computer and network, teaches you how to speak the lingo of both hackers and security professionals, and outlines the broad strokes of what it takes to secure your computer and your network.
In this book, you will learn how to secure both individual computers and entire networks. You will also find out how to secure data transmission, and you will complete an exercise to find out about your region’s laws regarding computer security. Perhaps the most crucial discussion in this chapter is what attacks are commonly attempted and how they are perpetrated. In this first chapter we set the stage for the rest of the book by outlining what exactly the dangers are and introducing you to the terminology used by both network security professionals and hackers. All of these topics are explored more fully in subsequent chapters.
How Seriously Should You Take Threats to Network Security?
The first step in understanding computer and network security is to formulate a realistic assessment of the threats to those systems. You will need a clear picture of the dangers in order to adequately prepare a defense. There seem to be two extreme attitudes regarding computer security. The first group assumes there is no real threat. Subscribers to this belief feel that there is little real danger to computer systems and that much of the negative news is simply unwarranted panic. They often believe taking only minimal security precautions should ensure the safety of their systems. The prevailing sentiment is, if our organization has not been attacked so far, we must be secure. If decision makers subscribe to this point of view, they tend to push a reactive approach to security. They will wait to address security issues until an incident occurs—the proverbial “closing the barn door after the horse has already gotten out.” If you are fortunate, the incident will have only minor impact on your organization and will serve as a much-needed wakeup call. If you are unfortunate, then your organization may face serious and possible catastrophic consequences. One major goal of this book is to encourage a proactive approach to security.
People who subscribe to the opposite viewpoint overestimate the dangers. They tend to assume that numerous talented hackers are an imminent threat to their system. They may believe that any teenager with a laptop can traverse highly secure systems at will. Such a worldview makes excellent movie plots, but it is simply unrealistic. The reality is that many people who call themselves hackers are less knowledgeable than they think they are. These people have a low probability of being able to compromise any system that has implemented even moderate security precautions.
This does not mean that skillful hackers do not exist, of course. However, they must balance the costs (financial, time) against the rewards (ideological, monetary). “Good” hackers tend to target systems that yield the highest rewards. If a hacker doesn’t perceive your system as beneficial to these goals, he is less likely to expend the resources to compromise your system. It is also important to understand that real intrusions into a network take time and effort. Hacking is not the dramatic process you see in movies. I often teach courses in hacking and penetration testing, and students are usually surprised to find that the process is actually a bit tedious and requires patience.
Both extremes of attitudes regarding the dangers to computer systems are inaccurate. It is certainly true that there are people who have the understanding of computer systems and the skills to compromise the security of many, if not most, systems. A number of people who call themselves hackers, though, are not as skilled as they claim to be. They have ascertained a few buzzwords from the Internet and may be convinced of their own digital supremacy, but they are not able to affect any real compromises to even a moderately secure system.
The truly talented hacker is no more common than the truly talented concert pianist. Consider how many people take piano lessons at some point in their lives. Now consider how many of those ever truly become virtuosos. The same is true of computer hackers. There are many people with mediocre skills, but truly skilled hackers are not terribly common. Keep in mind that even those who do possess the requisite skills need to be motivated to expend the time and effort to compromise your system.
A better way to assess the threat level to your system is to weigh the attractiveness of your system to potential intruders against the security measures in place. This is the essence of threat analysis. You examine your risks, vulnerabilities, and threats in order to decide where to put the most effort in cybersecurity.
Keep in mind, too, that the greatest external threat to any system is not hackers but malware and denial of service (DoS) attacks. Malware includes viruses, worms, Trojan horses, and logic bombs. And beyond the external attacks, there is the issue of internal problems due to malfeasance or simple ignorance.
Security audits always begin with a risk assessment, and that is what we are describing here. First you need to identify your assets. Clearly, the actual computers, routers, switches and other devices that make up your network are assets. But it is more likely that your most important assets lie in the information on your network. Identifying assets begins with evaluating the information your network stores and its value. Does your network contain personal information for bank accounts? Perhaps medical information, health care records? In other cases, your network might contain intellectual property, trade secrets, or even classified military data.
Once you have identified the assets, you need to take inventory of the threats to your assets. Certainly, any threat is possible, but some are more likely than others. This is very much like what one does when selecting home insurance. If you live in a flood plain, then flood insurance is critical. If you live at a high altitude in a desert, it may be less critical. We do the same thing with our data. If you are working for a defense contractor, then foreign state-sponsored hackers are a significant threat. However, if you are the network administrator for a school district, then your greatest threat is likely to be juveniles attempting to breach the network. It is always important to realize what the threats are for your network.
Once you have identified your assets and inventoried the threats, you need to find out what vulnerabilities your system has. Every system has vulnerabilities. Identifying your network’s specific vulnerabilities is a major part of risk assessment.
The knowledge of your assets, threats, and vulnerabilities will give you the information needed to decide what security measures are appropriate for your network. You will always have budget constraints, so you need to make wise decisions in selecting security controls. Using good risk assessment is how you make wise security decisions.
There are methods and formulas for quantifying risk. A few simple formulas are provided here. In order to calculate the loss from a single incident, you multiply the asset value by the percentage of that asset that is exposed:
Single Loss Expectancy (SLE) = Asset Value (AV) × Exposure Factor (EF)
What this formula means is that in order to calculate the loss from a single incident, you start with the asset value, and multiple that times what percentage of that asset is exposed. Let us assume you have a laptop that was purchased for $1000. It has depreciated by 20%, meaning there is 80% of its value left. If that laptop is lost or stolen, $1000 (AV) × .8 (EV) = $800 (SLE). Now this is rather oversimplified and does not account for the value of the data. But it does illustrate the point of the formula. Now to go forward and calculate the loss per year, you use the following formula:
Annualized Loss Expectancy (ALE) = Single Loss Expectancy (SLE) × Annual Rate of Occurrence (ARO)
Using the previous SLE of $800, if you expect to lose 3 laptops per year, then the ARO = $800 × 3, or $2400.
Obviously, these formulas have some subjectiveness to them. (For example, ARO is usually estimated from industry trends and past incidents.) But they can help you to understand the risk you have. This will help to guide you in determining what resources to allocate to addressing the risk.
Once you have identified a risk, you really have only four choices:
Acceptance: This means you find the impact of the risk to be less than the cost of addressing it, or the probability is so remote that you do nothing. This is not the most common approach but is appropriate in some scenarios.
Avoidance: This means ensuring that there is zero chance of the risk occurring. If you are concerned about a virus being introduced to your network via USB and you shut down all USB ports, you have avoided the risk.
Transference: This involves transferring responsibility for the damages should the risk be realized. This is commonly done via cyber threat insurance.
Mitigation: With this approach, which is the most common approach, you take steps to reduce either the likelihood of the event occurring or the impact. For example, if you are concerned about computer viruses, you might mitigate that via antivirus software and policies about attachments and links.
This is basic risk assessment. Before spending resources to address a threat, you must do this type of basic threat assessment. How likely is the threat to be realized? If it is realized, how much damage would it cause you? For example, I personally don’t employ any security on my website. Yes, someone could hack it, but if they did, the impact would be negligible. There is no data on that website at all—no database back end, no files, no logins, and so on. The only information on the website is information I freely give to anyone, without even recording who gets the information. Thus, for this website, the impact of a breach is only negligible, thus making expenditure of resources on security unacceptable. At the other extreme are major e-commerce sites. These sites invest a great deal of resources on security because breach of such a website would immediately cost significant money and damage the organization’s reputation in the long term.
Identifying Types of Threats
As discussed in the previous section, identifying your threats is a key part of risk assessment. Some threats are common to all networks; others are more likely with specific types of networks. Various sources have divided threats into different categories based on specific criteria. In this section we will examine threats that have been divided into categories based on the nature of the attack. Most attacks can be categorized as one of seven broad classes:
Malware: This is a generic term for software that has a malicious purpose. It includes virus attacks, worms, adware, Trojan horses, and spyware. This is the most prevalent danger to your system. One reason the relatively generic term malware is now widely used is that many times a piece of malware does not fit neatly into one of these categories.
Security breaches: This group of attacks includes any attempt to gain unauthorized access to your system. This includes cracking passwords, elevating privileges, breaking into a server…all the things you probably associate with the term hacking.
DoS attacks: These are designed to prevent legitimate access to your system. And, as you will see in later chapters, this includes distributed denial of service (DDoS).
Web attacks: This is any attack that attempts to breach your website. Two of the most common such attacks are SQL injection and cross-site scripting.
Session hijacking: These attacks are rather advanced and involve an attacker attempting to take over a session.
Insider threats: These are breaches based on someone who has access to your network misusing his access to steal data or compromise security.
DNS poisoning: This type of attack seeks to compromise a DNS server so that users can be redirected to malicious websites, including phishing websites.
There are other attacks, such as social engineering. The foregoing list is just an attempt to provide a broad categorization of attack types. This section offers a broad description of each type of attack. Later chapters go into greater detail on each specific attack, how it is accomplished, and how to avoid it.
Malware
Malware is a generic term for software that has a malicious purpose. This section discusses four types of malware: viruses, Trojan horses, spyware, and logic bombs. Trojan horses and viruses are the most widely encountered. One could also include rootkits in the malware category, but these usually spread as viruses and thus are regarded as simply a specific type of virus.
According to Malwarebytes:
Malware, or “malicious software,” is an umbrella term that describes any malicious program or code that is harmful to systems. Hostile, intrusive, and intentionally nasty, malware seeks to invade, damage, or disable computers, computer systems, networks, tablets, and mobile devices, often by taking partial control over a device’s operations. Like the human flu, it interferes with normal functioning.”3
We still think primarily of computer viruses when we think of malware. The key characteristic of a computer virus is that it self-replicates. A computer virus is similar to a biological virus; both are designed to replicate and spread. The most common method for spreading a virus is using the victim’s email account to spread the virus to everyone in his address book. Some viruses don’t actually harm the system itself, but almost all of them cause network slowdowns due to the heavy network traffic caused by virus replication.
The Trojan horse gets its name from an ancient tale. The city of Troy was besieged for an extended period of time. The attackers could not gain entrance, so they constructed a huge wooden horse and one night left it in front of the gates of Troy. The next morning the residents of Troy saw the horse and assumed it to be a gift, so they rolled the wooden horse into the city. Unbeknownst to them, several soldiers were hidden inside the horse. That evening the soldiers left the horse, opened the city gates, and let their fellow attackers into the city. An electronic Trojan horse works similarly, appearing to be benign software but secretly downloading a virus or some other type of malware onto a computer from within.
Another category of malware currently on the rise is spyware. Spyware is simply software that literally spies on what you do on your computer. Spyware can be as simple as a cookie—a text file that your browser creates and stores on your hard drive—that a website you have visited downloads to your machine and uses to recognize you when you return to the site. However, that flat file can then be read by the website or by other websites. Any data that the file saves can be retrieved by any website, so your entire Internet browsing history can be tracked. Spyware may also consist of software that takes periodic screenshots of the activity on your computer and sends them to the attacker.
Another form of spyware, called a key logger, records all of your keystrokes. Some key loggers also take periodic screenshots of your computer. Data is then either stored for later retrieval by the person who installed the key logger or is sent immediately back via email. We will discuss specific types of key loggers later in this book.
A logic bomb is software that lays dormant until some specific condition is met. That condition is usually a date and time. When the condition is met, the software does some malicious act, such as delete files, alter system configuration, or perhaps release a virus. In Chapter 5, “Malware,” we will examine logic bombs and other types of malware in detail.
Compromising System Security
Next we will look at attacks that breach your system’s security. This activity is commonly referred to as hacking, though that is not the term hackers themselves use. We will delve into appropriate terminology in just a few pages; however, it should be noted at this point that cracking is the appropriate word for intruding into a system without permission, usually with malevolent intent. Any attack that is designed to breach your security, either via some operating system flaw or any other means, can be classified as cracking.
Essentially any technique to bypass security, crack passwords, breach Wi-Fi, or in any way actually gain access to the target network fits into this category. That makes this a very broad category indeed.
However, not all breaches involve technical exploits. In fact, some of the most successful breaches are entirely nontechnical. Social engineering is a technique for breaching a system’s security by exploiting human nature rather than technology. This was the path that the famous hacker Kevin Mitnick most often used. Social engineering uses standard con techniques to get users to give up the information needed to gain access to a target system. The way this method works is rather simple: The perpetrator gets preliminary information about a target organization and leverages it to obtain additional information from the system’s users.
Following is an example of social engineering in action. Armed with the name of a system administrator, you might call someone in the business’s accounting department and claim to be one of the company’s technical support personnel. Mentioning the system administrator’s name would help validate that claim, allowing you to ask questions in an attempt to ascertain more details about the system’s specifications. A savvy intruder might even get the accounting person to say a username and password. As you can see, the success of this method is based on how well the prospective intruder can manipulate people and actually has little to do with computer skills.
The growing popularity of wireless networks gave rise to new kinds of attacks. One such activity is war-driving. This type of attack is an offshoot of war-dialing. With war-dialing, a hacker sets up a computer to call phone numbers in sequence until another computer answers to try to gain entry to its system. War-driving is much the same concept, applied to locating vulnerable wireless networks. In this scenario, the hacker simply drives around trying to locate wireless networks. Many people forget that their wireless network signal often extends as much as 100 feet (thus, past walls). At the 2004 DEF CON convention for hackers, there was a war-driving contest where contestants drove around the city trying to locate as many vulnerable wireless networks as they could. These sorts of contests are now common at various hacking conventions. (DEF CON is the largest and oldest hacking conference in the world.)
Recent technological innovations have introduced new variations of war driving/dialing. Now we have war flying. The attacker uses a small private drone equipped with Wi-Fi sniffing and cracking software, flies the drone in the area of interest, and attempts to gain access to wireless networks.
Of course, Wi-Fi hacking is only one sort of breach. Password cracking tools are now commonly available on the Internet. We will examine some of these later in this book. There are also exploits of software vulnerabilities that allow one to gain access to the target computer.
DoS Attacks
In a DoS, the attacker does not actually access the system. Rather, this person simply blocks access from legitimate users. One common way to prevent legitimate service is to flood the targeted system with so many false connection requests that the system cannot respond to legitimate requests. DoS is a very common attack because it is so easy.
In recent years a proliferation of DoS tools have been available on the Internet. One of the most common such tools is the Low Orbit Ion Cannon (LOIC). Because these tools can be downloaded for free from the Internet, anyone can execute a DoS attack, even without technical skill.
We also have variations, such as the DDoS attack. This attack uses multiple machines to attack the target. Given that many modern websites are hosted in network clusters or even in clouds, it is very difficult for a single attacking machine to generate enough traffic to take down a web server. But a network of hundreds or even thousands of computers certainly can. We will explore DoS and DDoS attacks in more detail in Chapter 4, “Denial of Service Attacks.”
Web Attacks
By their nature, web servers have to allow communications. Oftentimes, websites allow users to interact with the website. Any part of a website that allows for user interaction is also a potential point for attempting a web-based attack. SQL injections involve entering SQL (Structured Query Language) commands into login forms (username and password text fields) in an attempt to trick the server into executing those commands. The most common purpose is to force the server to log the attacker on, even though the attacker does not have a legitimate username and password. While SQL injection is just one type of web attack, it is the most common.
SQL Injection
SQL injection is still quite common, though it has been known for many years. Unfortunately, not enough web developers take the appropriate steps to remediate the vulnerabilities that make such an attack possible. Given the prevalence of this type of attack, it warrants a bit more detailed description.
Consider one of the simplest forms of SQL injection, used to bypass login screens. The website was developed in some web programming language, such as PHP or ASP.NET. The database is most likely a basic relational database such as Oracle, SQL Server, MySQL, or PostgreSQL is used to communicate with the database, so we need to put SQL statements into the web page that was written into some programming language. That will allow us to query the database and see if the username and password are valid.
SQL is relatively easy to understand; in fact, it looks a lot like English. There are commands like SELECT to get data, INSERT to put data in, and UPDATE to change data. In order to log in to a website, the web page has to query a database table to see if that username and password are correct. The general structure of SQL is like this:
select column1, column2 from tablename
or:
select * from tablename; Conditions: select columns from tablename where condition;
For example:
SELECT * FROM tblUsers WHERE USERNAME = 'jsmith'
This statement retrieves all the columns or fields from a table named tblUsers where the username is jsmith.
The problem arises when we try to put SQL statements into our web page. Recall that the web page was written in some web language such as PHP or ASP.NET. If you just place SQL statements directly in the web page code, an error will be generated. The SQL statements in the programming code for the website have to use quotation marks to separate the SQL code from the programming code. A typical SQL statement might look something like this:
"SELECT * FROM tblUsers WHERE USERNAME = '" + txtUsername.Text +' AND PASSWORD = '" + txtPassword.Text +"'" .
If you enter username 'jdoe' and the password 'password', this code produces this SQL command:
SELECT * FROM tblUsers WHERE USERNAME = 'jdoe' AND PASSWORD = 'password'
This is fairly easy to understand even for nonprogrammers. And it is effective. If there is a match in the database, that means the username and password match. If no records are returned from the database, that means there was no match, and this is not a valid login.
The most basic form of SQL injection seeks to subvert this process. The idea is to create a statement that will always be true. For example, instead of putting an actual username and password into the appropriate text fields, the attacker will enter ' or '1' = '1 into the username and password boxes. This will cause the program to create this query:
SELECT * FROM tblUsers WHERE USERNAME = '' or '1' = '1' AND PASSWORD = '' or '1' = '1'.
So you are telling the database and application to return all records where username and password are blank or if 1 = 1. It is highly unlikely that the username and password are blank. But I am certain that 1 = 1 always. Any true statement can be substituted. Examples are a = a and bob = bob.
The tragedy of this attack is that it is so easy to prevent. If the web programmer would simply filter all input prior to processing it, then this type of SQL injection would be impossible. Filtering means that before any user input is processed, the web page programming code looks through that code for common SQL injection symbols, scripting symbols, and similar items. It is true that each year fewer and fewer websites are susceptible to these attacks. However, there are still many sites that are vulnerable. SQL injection is still one of the top vulnerabilities found in websites according to OWASP (The Open Web Application Security Project). Subsequent chapters provide more coverage of most of these attacks, including tools used for them.
Cross-Site Scripting
Cross-site scripting is a type of attack that is closely related to SQL injection. It involves entering data other than what was intended, and its success depends on the web programmer not filtering input. The perpetrator finds some area of a website that allows users to type in text that other users will see and then instead injects client-side script into those fields.
To better understand this process, let’s look at a hypothetical scenario. Let’s assume that ABC Online Book Sales has a website. In addition to shopping, users can have accounts with credit cards stored, post reviews, and more. The attacker first sets up an alternate web page that looks as close to the real one as possible. Then the attacker goes to the real ABC Online Book Sales website and finds a rather popular book. He goes to the review section, but instead of typing in a review, he types in this:
<script> window.location = "http://www.fakesite.com"; </script>
Now when users go to that book, this script will redirect them to the fake site, which looks a great deal like the real one. The attacker then can have the website tell the user that his session has timed out and to please log in again. That would allow the attacker to gather a lot of account and password information. That is only one scenario, but it illustrates the attack.
Session Hijacking
Performing session hijacking can be rather complex. For that reason, it is not a very common form of attack. Simply put, the attacker monitors an authenticated session between the client machine and the server and takes over that session. We will explore specific methods of how this is done later in this book.
A 1985 paper written by Robert T. Morris, titled “A Weakness in the 4.2BSD Unix TCP/IP Software,” defined the original session hijacking. By predicting the initial sequence number, Morris was able to spoof the identity of a trusted client to a server. This is much harder to do today.
In addition to flags (syn, ack, syn-ack), the packet header will contain the sequence number that is intended to be used by the client to reconstitute the data sent over the stream in the correct order. (We will explore network packet flags in Chapter 2, “Networks and the Internet.”)
The Morris attack and several other session hijacking attacks require the attacker to be connected to the network and to simultaneously knock the legitimate user offline and then pretend to be that user. As you can probably imagine, it is a complex attack.
Insider Threats
Insider threats are a type of security breach. However, they present such a significant issue that we will deal with them separately. An insider threat occurs when someone inside your organization either misuses his access to data or accesses data he is not authorized to access.
The most obvious case is that of Edward Snowden. For our purposes, we can ignore the political issues connected with his case and instead focus solely on the issue of insiders accessing information and using it in a way other than what was authorized.
In 2009 Edward Snowden was working as a contractor for Dell, which manages computer systems for several U.S. government agencies. In March 2012 he was assigned to an NSA location in Hawaii. While there he convinced several people at that location to provide him with their login and password information, under the pretense of performing network administrative duties. Some sources dispute whether or not this is the specific method he used, but it is the one most widely reported. Whatever method he used, he accessed and downloaded thousands of documents that he was not authorized to access.
Again, ignoring the political issues and the content of the documents, our focus is on the security issues. Clearly, there were inadequate security controls in place to detect Edward Snowden’s activities and to prevent him from disclosing the content of confidential documents. While your organization may not have the high profile that the NSA has, any organization is susceptible to insider threats. Theft of trade secrets by insiders is a common business concern and has been the focus of many lawsuits against former employees. In both Chapter 7, “Industrial Espionage in Cyberspace,” and Chapter 9, “Computer Security Technology,” we will see some countermeasures to mitigate this threat.
While Edward Snowden is an obvious example of insider threats, that is only one example. A common scenario is when someone who has legitimate access to some particular source of data chooses either to access data he is not authorized to access or to use the data in a manner other than how he has been authorized to use it. Here are a few examples:
A hospital employee who accesses patient records to use the data to steal a patient’s identity, or someone with no access at all who accesses records
A salesperson who takes a list of contacts with him when he leaves the company
This is actually a much greater problem than many people appreciate. Within an organization, information security is often more lax than it should be. Most people are more concerned with external security than internal security, so it is often rather easy to access data within an organization. In my career as a security consultant, I have seen networks where sensitive data is simply placed on a shared drive with no limiting of access to it. That means anyone on the network can access that data. In a case such as this, when information is taken, no crime has been committed. However, in other cases, employees purposefully circumvent security measures to access data they are not authorized to. The most common method is to simply log in with someone else’s password. That enables the perpetrator to access the resources and data to which that other person has been granted access. Unfortunately, many people use weak passwords or, worse, they write their password somewhere on their desk. Some users even share passwords. For example, suppose a sales manager is out sick but wants to check to see if a client has emailed her. So she calls her assistant and gives him her login so he can check her email. This sort of behavior should be strictly prohibited by company security policies, but it still occurs. The problem is that now two people have the sales manager’s login. Either one could use it or reveal it to someone else (accidentally or on purpose). So there is a greater chance of someone using that manager’s login to access data he has not been authorized to access.
DNS Poisoning
Most of your communication on the Internet will involve DNS, or Domain Name System. DNS is what translates the domain names you and I understand (like www.ChuckEasttom.com) into IP addresses that computers and routers understand. DNS poisoning uses one of several techniques to compromise that process and redirect traffic to an illicit site, often for the purpose of stealing personal information.
Here is one scenario whereby an attacker might execute a DNS poisoning attack: First the attacker creates a phishing website. It spoofs a bank that we will call ABC Bank. The attacker wants to lure users there so he can steal their passwords and use them on the real bank website. Since many users are too smart to click on links, he will use DNS poisoning to trick them.
The attacker creates his own DNS server. (Actually, this part is relatively easy.) Then he puts two records in that DNS server. The first is for the ABC Bank website, pointing to his fake site rather than the real bank site. The second entry is for a domain that does not exist. The attacker can search domain registries until he finds one that does not exist. For illustration purposes, we will refer to this as XYZ domain.
Then the attacker sends a request to a DNS server on the target network. That request purports to be from any IP address within the target network and is requesting the DNS server resolve the XYZ domain.
Obviously, the DNS server does not have an entry for the XYZ domain since it does not exist. So, it begins to propagate the request up its chain of command and eventually to its service provider DNS server. At any point in that process, the attacker sends a flood of spoofed responses claiming to be from a DNS server that the target server is trying to request records from but that are actually coming from his DNS server and offering the IP address for XYZ domain. At that point the hacker’s DNS server offers to do a zone transfer, exchanging all information with the target server. That information includes the spoofed address for ABC Bank. Now the target DNS server has an entry for ABC Bank that points to the hacker’s website rather than the real ABC Bank website. Should users on that network type in the URL for ABC Bank, their own DNS server will direct them to the hacker’s site.
This attack, like so many, depends on vulnerabilities in the target system. A properly configured DNS server should never perform a zone transfer with any DNS server that is not already authenticated in the domain. However, the unfortunate fact is that there are plenty of DNS servers that are not properly configured.
New Attacks
Many of the threats discussed in the first three editions of this book are still plaguing network security. Malware, DoS, and other such attacks are just as common today as they were 5 years ago or even 10 years ago.
One new phenomenon is doxing, which is the process of finding personal information about an individual and broadcasting it, often via the Internet. This can be any personal information about any person. However, it is most often used against public figures. It has even been the case that a previous director of the CIA was the target of doxing.4
Hacking of medical devices is another new type of attack. Hacker Barnaby Jack first revealed a vulnerability in an insulin pump that could allow an attacker to take control of the pump and cause it to dispense the entire reservoir of insulin in a single does, thus killing the patient. To date there are no confirmed incidents of this having actually been done, but it is disturbing nonetheless. Similar security flaws have been found in pacemakers. In 2018, the U.S. Food and Drug Administration (FDA) published a list of medical devices that are not secure. So, this problem appears to be getting worse.
In July 2015 it was revealed that Jeep vehicles could be hacked and shut down during normal operation. This means that a hacker could cause a Jeep to stop in the middle of heavy, high-speed traffic, potentially causing a serious automobile accident. The hacking of cars has become more widespread. DEF CON in 2016 had a car hacking village.
More recently, the Internet of Things has created a new set of targets for attackers. Smart homes and offices, with their integrated Internet-enabled devices, make attractive targets for attackers. For example, ransomware has been created for smart thermostats.
All of these attacks show a common theme: As our lives become more interconnected with technology, new vulnerabilities emerge. Some of these vulnerabilities are not merely endangering data and computer systems but potentially endangering lives.
Assessing the Likelihood of an Attack on Your Network
How likely are these attacks? What are the real dangers facing you as an individual or your organization? What are the most likely attacks, and what are your vulnerabilities? Let’s take a look at what threats are out there and which ones are the most likely to cause you or your organization problems.
At one time, the most likely threat to individuals and large organizations was the computer virus. And it is still true that in any given month, several new virus outbreaks will be documented. New viruses are being created all the time, and old ones are still out there. However, there are other very common attacks, such as spyware. Spyware is quickly becoming an even bigger problem than viruses.
After viruses, the most common attack is unauthorized usage of computer systems. Unauthorized usage includes everything from DoS attacks to outright intrusion of your system. It also includes internal employees misusing system resources. The first edition of this book referenced a survey by the Computer Security Institute of 223 computer professionals showing over $445 million in losses due to computer security breaches. In 75% of the cases, an Internet connection was the point of attack, while 33% of the professionals cited the location as their internal systems. A rather astonishing 78% of those surveyed detected employee abuse of systems/Internet. This statistic means that in any organization, one of the chief dangers might be its own employees. In 2019 similar threats still exist, with only slight changes in the percentages.
The 2014 Data Breach Investigation Report from Verizon surveyed 63,437 security incidents with 1367 confirmed breaches in 95 countries. This survey showed significant employee abuse of the network as well as many of the familiar attacks we have already discussed in this chapter. The 2015 Data Breach Investigation Report did not show significant improvement. In 2019, the situation was not improved. In fact, as mentioned earlier in the chapter, it is expected that cybercrime will cost more than $1 trillion per year.
Basic Security Terminology
Before you embark on the rest of this chapter and this book, it is important to know some basic terminology. The security and hacking terms in this section provide a basic introduction to computer security terminology, but they are an excellent starting point to help you prepare for learning more about computer security. Additional terms will be introduced throughout the text and listed in the Glossary at the end of this book.
The world of computer security takes its vocabulary from both the professional security community and the hacker community.
Hacker Slang
You probably have heard the term hacker used in movies and in news broadcasts. Most people use it to describe any person who breaks into a computer system. In the hacking community, however, a hacker is an expert on a particular system or systems, a person who simply wants to learn more about the system. Hackers feel that looking at a system’s flaws is the best way to learn about that system. For example, someone well versed in the Linux operating system who works to understand that system by learning its weaknesses and flaws would be a hacker.
This process does often mean seeing if a flaw can be exploited to gain access to a system. This “exploiting” part of the process is where hackers differentiate themselves into three groups:
A white hat hacker, upon finding some flaw in a system, will report the flaw to the vendor of that system. For example, if a white hat hacker were to discover some flaw in Red Hat Linux, he would email the Red Hat company (probably anonymously) and explain exactly what the flaw is and how it was exploited. White hat hackers are often hired specifically by companies to do penetration tests. The EC Council even has a certification test for white hat hackers: the Certified Ethical Hacker test.
A black hat hacker is the person normally depicted in the media. Once she gains access to a system, her goal is to cause some type of harm. She might steal data, erase files, or deface websites. Black hat hackers are sometimes referred to as crackers.
A gray hat hacker is normally a law-abiding citizen but in some cases will venture into illegal activities.
Regardless of how hackers view themselves, intruding on any system is illegal. This means that technically speaking all hackers, regardless of the color of the metaphorical hat they may wear, are in violation of the law. However, many people feel that white hat hackers actually perform a service by finding flaws and informing vendors before those flaws are exploited by less ethically inclined individuals.
Script Kiddies
A hacker is an expert in a given system. As with any profession, it includes its share of frauds. So, what is the term for someone who calls himself a hacker but lacks the expertise? The most common term for this sort of person is script kiddy). Yes, that is an older resource, but the term still means the same thing. The name comes from the fact that the Internet is full of utilities and scripts that one can download to perform some hacking tasks. Many of these tools have easy-to-use graphical user interfaces that allow those with very little or no skill to operate them. A classic example is the Low Orbit Ion Cannon tool for executing a DoS attack. Someone who downloads such a tool without really understanding the target system is considered a script kiddy. A significant number of the people you are likely to encounter who call themselves hackers are, in reality, mere script kiddies.
Ethical Hacking: Penetration Testers
When and why would someone give permission to another party to hack his system? The most common answer is in order to assess system vulnerabilities. Such a person used to be called a sneaker, but now the term penetration tester is far more widely used. Whatever the term, the person legally breaks into a system in order to assess security deficiencies, as portrayed in the 1992 film Sneakers, starring Robert Redford, Dan Aykroyd, and Sidney Poitier. More and more companies are soliciting the services of such individuals or firms to assess their vulnerabilities.
Anyone hired to assess the vulnerabilities of a system should be both technically proficient and ethical. Run a criminal background check and avoid those people with problematic pasts. There are plenty of legitimate security professionals available who know and understand hacker skills but have never committed security crimes. If you take to its logical conclusion the argument that hiring convicted hackers means hiring talented people, you could surmise that obviously those in question are not as good at hacking as they would like to think because they were caught.
Most importantly, giving a person with a criminal background access to your systems is on par with hiring a person with multiple DWI convictions to be your driver. In both cases, you are inviting problems and perhaps assuming significant civil liabilities.
Also, some review of their qualifications is clearly in order. Just as there are people who claim to be highly skilled hackers yet are not, there are those who will claim to be skilled penetration testers yet lack the skills truly needed. You would not want to inadvertently hire a script kiddy who thinks she is a penetration tester. Such a person might then pronounce your system quite sound when, in fact, it was simply a lack of skills that prevented the script kiddy from successfully breaching your security. Later in this book, in Chapter 11, “Network Scanning and Vulnerability Scanning,” we discuss the basics of assessing a target system. In Chapter 11 we also discuss the qualifications you should seek in any consultant you might hire for this purpose.
Phreaking
One specialty type of hacking involves breaking into telephone systems. This subspecialty of hacking is referred to as phreaking. The New Hacker’s Dictionary actually defines phreaking as “the action of using mischievous and mostly illegal ways in order to not pay for some sort of telecommunications bill, order, transfer, or other service” Phreaking requires a rather significant knowledge of telecommunications, and many phreakers have some professional experience working for a phone company or other telecommunications business. Often this type of activity is dependent upon specific technology required to compromise phone systems more than simply knowing certain techniques.
Professional Terms
Most hacker terminology, as you may have noticed, is concerned with the activity (phreaking) or the person performing the activity (penetration tester). In contrast, security professional terminology describes defensive barrier devices, procedures, and policies. This is quite logical because hacking is an offensive activity centered on attackers and attack methodologies, whereas security is a defensive activity concerned with defensive barriers and procedures.
Security Devices
The most basic security device is the firewall. A firewall is a barrier between a network and the outside world. Sometimes a firewall takes the form of a standalone server, sometimes a router, and sometimes software running on a machine. Whatever its physical form, a firewall filters traffic entering and exiting the network. A proxy server is often used with a firewall to hide the internal network’s IP address and present a single IP address (its own) to the outside world.
Firewalls and proxy servers guard the perimeter by analyzing traffic (at least inbound traffic and in many cases outbound traffic as well) and blocking traffic that has been disallowed by the administrator. These two safeguards are often augmented by an intrusion detection system (IDS). An IDS simply monitors traffic, looking for suspicious activity that might indicate an attempted intrusion. We will examine these technologies and others in Chapter 9.
Security Activities
In addition to devices, there are security activities. Authentication is the most basic security activity. It is merely the process of determining if the credentials given by a user or another system (such as a username and password) are authorized to access the network resource in question. When you log in with your username and password, the system will attempt to authenticate that username and password. If it is authenticated, you will be granted access.
Another crucial safeguard is auditing, which is the process of reviewing logs, records, and procedures to determine if these items meet standards. This activity will be mentioned in many places throughout this book and will be a definite focus in a few chapters.
The security and hacking terms that we have just covered are only an introduction to computer security terminology, but they provide an excellent starting point that will help you prepare for learning more about computer security. Additional terms will be introduced throughout the text as needed and compiled in the Glossary at the end of the book.
Concepts and Approaches
The approach you take toward security influences all subsequent security decisions and sets the tone for the entire organization’s network security infrastructure. Before we delve into various network security paradigms, let us take a moment to examine a few concepts that should permeate your thinking about security.
The first concept is the CIA triangle. This does not refer to clandestine operations involving the Central Intelligence Agency; rather, it is a reference to the three pillars of security: confidentiality, integrity, and availability. When you are thinking about security, your thought processes should always be guided by these three principles. First and foremost, are you keeping the data confidential? Does your approach help guarantee the integrity of data? And does your approach still make the data readily available to authorized users?
While the CIA triangle is a staple of all security courses and certifications, more sophisticated models have been developed. A multi-faceted approach to describing security is found in The McCumber cube. The McCumber cube is a way of evaluating security of a network, looking at all aspects. It was described in detail in 2004 in the book Assessing and Managing Security Risk in IT Systems: A Structured Methodology. It looks at security as a three-dimensional cube. The dimensions are goals, information states, and safeguards. The McCumber cube has the advantage of being a natural expansion of the CIA triangle into three dimensions. This is advantageous because the CIA triangle is widely known and understood in the cyber-security community. This makes the transition to the McCumber cube, and subsequently a taxonomy based on the McCumber cube, easier. Any taxonomy must be readily learned and applied by security professionals in order to be effective. You can see the McCumber cube in Figure 1.1:
Figure 1.1 The McCumber cube
Another important concept to keep in mind is least privileges. This means that each user or service running on your network should have the least number of privileges/access required to do her job. No one should be granted access to anything unless it is absolutely required for the job.
Network security paradigms can be classified based on either the scope of security measures taken (perimeter, layered) or how proactive the system is.
In a perimeter security approach, the bulk of security efforts are focused on the perimeter of the network. This focus might include firewalls, proxy servers, password policies, or any technology or procedure to make unauthorized access of the network less likely. Little or no effort is put into securing the systems within the network. In this approach, the perimeter is secured, but the various systems within that perimeter are often vulnerable.
There are additional issues regarding perimeter security that include physical security. These issues can include fences, closed-circuit TV, guards, locks, and so on, depending on the security needs of the organization.
The perimeter approach is clearly flawed, so why do some companies use it? Small organizations might use the perimeter approach if they have budget constraints or inexperienced network administrators. A perimeter method might be adequate for small organizations that do not store sensitive data, but it rarely works in a larger corporate setting.
A layered security approach is one in which not only is the perimeter secured, but individual systems within the network are also secured. All servers, workstations, routers, and hubs within the network are secure. One way to accomplish this is to divide the network into segments and secure each segment as if it were a separate network, so if the perimeter security is compromised, not all the internal systems are affected. This is the preferred method and should be used whenever possible.
You should also measure your security approach by how proactive/reactive it is. This is done by gauging how much of the system’s security infrastructure and policies are dedicated to preventive measures and how much of the security system is designed to respond to attack. A passive security approach takes few or no steps to prevent an attack. A dynamic or proactive defense is one in which steps are taken to prevent attacks before they occur.
One example of this defense is the use of IDSs, which work to detect attempts to circumvent security measures. These systems can tell a system administrator that an attempt to breach security has been made, even if that attempt is not successful. IDSs can also be used to detect various techniques intruders use to assess a target system, thus alerting a network administrator to the potential for an attempted breach before the attempt is even initiated.
In the real world, network security is usually not completely in one paradigm or another; it is usually a hybrid approach. Networks generally include elements of both security paradigms. The two categories also combine. One can have a network that is predominantly passive but layered or one that is primarily perimeter but proactive. It can be helpful to consider approaches to computer security along a Cartesian coordinate system, as illustrated in Figure 1.2, with the x axis representing the level of passive–active approaches and the y axis depicting the range from perimeter to layered defense.
Figure 1.2 The security approach guide.
The most desirable hybrid approach is a layered paradigm that is dynamic—that is, in the upper-right quadrant of the figure.
How Do Legal Issues Impact Network Security?
An increasing number of legal issues affect how one approaches computer security. If your organization is a publicly traded company or a government agency or does business with either one, there may be legal constraints regarding your network security. Even if your network is not legally bound to these security guidelines, it’s useful to understand the various laws impacting computer security. You may choose to apply them to your own security standards.
One of the oldest pieces of legislation in the United States that affects computer security is the Computer Security Act of 1987. It requires government agencies to identify sensitive systems, conduct computer security training, and develop computer security plans. This law was a vague mandate ordering federal agencies in the United States to establish security measures, but it did not specify standards.
This legislation established a legal mandate to enact specific standards, paving the way for future guidelines and regulations. It also helped define terms, such as what information is considered “sensitive.” This quote is found in the legislation itself:
The term “sensitive information” means any information, the loss, misuse, or unauthorized access to or modification of which could adversely affect the national interest or the conduct of Federal programs, or the privacy to which individuals are entitled under section 552a of title 5, United States Code (the Privacy Act), but which has not been specifically authorized under criteria established by an Executive order or an Act of Congress to be kept secret in the interest of national defense or foreign policy.
This definition of the word sensitive should be kept in mind because it indicated that more than just Social Security information and medical history information must be secured.
When considering what information needs to be secured, simply answer this question: Would the unauthorized access or modification of this information adversely affect your organization? If the answer is yes, then you must consider that information sensitive and in need of security precautions.
Another more specific federal law that applied to mandated security for government systems was OMB Circular A-130 (specifically, Appendix III). This document required that federal agencies establish security programs containing specified elements. It also described requirements for developing standards for computer systems and for records held by government agencies.
Most states have specific laws regarding computer security, such as legislation like the Computer Crimes Act of Florida, the Computer Crime Act of Alabama, and the Computer Crimes Act of Oklahoma. If you’re responsible for network security, you might find yourself part of a criminal investigation. This could be an investigation into a hacking incident or employee misuse of computer resources. A list of computer crime laws (organized by state) can be found at http://criminal.findlaw.com/criminal-charges/cyber-crimes.html.
Online Security Resources
As you read this book, and when you move out into the professional world, you will have frequent need for additional security resources. Appendix A, “Resources,” includes a more complete list of resources, but this section highlights a few of the most important ones you may find useful now.
CERT
The Computer Emergency Response Team (CERT; www.cert.org) is sponsored by Carnegie-Mellon University. CERT was the first computer incident-response team, and it is still one of the most respected in the industry. Anyone interested in network security should visit the site routinely. On the website you will find a wealth of documentation, including guidelines for security policies, cutting-edge security research, and more.
Microsoft Security Advisor
Because so many computers today run Microsoft operating systems, another good resource is the Microsoft Security Advisor website: https://www.microsoft.com/en-us/msrc?rtc=1. This site is a portal to all Microsoft security information, tools, and updates. If you use any Microsoft software, you should visit this website regularly.
F-Secure
The F-Secure corporation maintains a website at www.f-secure.com. This site is, among other things, a repository for detailed information on virus outbreaks. Here you will find not only notifications about a particular virus but detailed information about the virus, such as how the virus spreads, and ways to recognize the virus, and, possibly, specific tools for cleaning an infected system of a particular virus.
SANS Institute
The SANS Institute website (www.sans.org) is a vast repository of security-related documentation. On this site you will find detailed documentation on virtually every aspect of computer security you can imagine. The SANS Institute also sponsors a number of security research projects and publishes information about those projects on its website.
Summary
Network security is a complex and constantly evolving field. Practitioners must stay on top of new threats and solutions and be proactive in assessing risk and protecting their networks. The first step to understanding network security is to become acquainted with the actual threats posed to a network. Without a realistic idea of what threats might affect your systems, you will be unable to effectively protect them. It is also critical that you acquire a basic understanding of the terminology used by both security professionals and those who would seek to compromise your security.
Test Your Skills
Multiple Choice Questions
You are trying to explain security to a nontechnical manager. She has taken a rather extreme view of computer security. Which of the following is one of the extreme viewpoints about computer security discussed in this chapter?
The federal government will handle security.
Microsoft will handle security.
There are no imminent dangers to your system.
There is no danger if you use Linux.
You have just taken over as network security administrator for a small community college. You want to take steps to secure your network. Before you can formulate a defense for a network, what do you need?
Appropriate security certifications
A clear picture of the dangers to be defended against
To finish this textbook
The help of an outside consultant
Mary is teaching an introductory cybersecurity course to freshmen. She is explaining to them the major threats. Which of the following is not one of the three major classes of threats?
Attempts to intrude on the system
Online auction fraud
Denial of service attacks
A computer virus
Being able to define attack terms is an important skill for a cybersecurity professional. What is a computer virus?
Any program that is downloaded to your system without your permission
Any program that self-replicates
Any program that causes harm to your system
Any program that can change your Windows Registry
Being able to define attack terms is an important skill for a cybersecurity professional. What is spyware?
Any software that monitors your system
Only software that logs keystrokes
Any software used to gather intelligence
Only software that monitors what websites you visit
What is a penetration tester?
A person who hacks a system without being caught
A person who hacks a system by faking a legitimate password
A person who hacks a system to test its vulnerabilities
A person who is an amateur hacker
Elizabeth is explaining various hacking terms to a class. She is in the process of discussing the history of phone system hacking. What is the term for hacking a phone system?
Telco-hacking
Hacking
Cracking
Phreaking
What is malware?
Software that has some malicious purpose
Software that is not functioning properly
Software that damages your system
Software that is not properly configured for your system
What is war-driving?
Driving and seeking a computer job
Driving while using a wireless connection for hacking
Driving looking for wireless networks to hack
Driving and seeking rival hackers
What is the name for the hacking technique that involves using persuasion and deception to get a person to provide information to help compromise security?
Social engineering
Conning
Human intel
Soft hacking
There are many threats on the Internet. Which one is currently the most common may change over time, but certain threats have always been more common than others. Which of the following is the most common threat on the Internet?
Auction fraud
Phreaking
Computer viruses
Illegal software
What are the three approaches to security?
Perimeter, layered, hybrid
High security, medium security, low security
Internal, external, and hybrid
Perimeter, complete, none
Defining your security strategy is an important step in securing a network. You are trying to classify devices based on the approach they take to security. An intrusion detection system is an example of which of the following?
Proactive security
Perimeter security
Hybrid security
Good security practices
Which of the following is the most basic security activity?
Authentication
Firewalls
Password protection
Auditing
The most desirable approach to security is one that is which of the following?
Perimeter and dynamic
Layered and dynamic
Perimeter and static
Layered and static
According to a survey of 223 computer professionals prepared by the Computer Security Institute, which of the following was most often cited as an issue by respondents?
Internal systems
Employee abuse
Routers
Internet connection
Which of the following types of privacy law affects computer security?
Any state privacy law
Any privacy law applicable to your organization
Any privacy law
Any federal privacy law
The first computer incident-response team is affiliated with what university?
Massachusetts Institute of Technology
Carnegie-Mellon University
Harvard University
California Technical University
Which of the following is the best definition of the term sensitive information?
Any information that has an impact on national security
Any information that is worth more than $1,000
Any information that if accessed by unauthorized personnel could damage your organization in any way
Any information that is protected by privacy laws
Which of the following is a major resource for detailed information on a computer virus?
The MIT Virus Library
The Microsoft Virus Library
The F-Secure Virus Library
The National Virus Repository
Exercises
Exercise 1.1: How Many Virus Attacks Have Occurred This Month?
Using some website resource, such as www.f-secure.com, look up recent computer virus outbreaks.
How many virus outbreaks have occurred in the past 7 days?
Write down how many outbreaks have occurred in the past 30 days, 90 days, and 1 year.
Are virus attacks increasing in frequency?
Exercise 1.2: Learning About Cookies as Spyware
Get an idea of what kind of information cookies store. You might find the following websites helpful:
Write a brief essay explaining in what way cookies can invade privacy.
Exercise 1.3: Hacker Terminology
Use the Hacker’s Dictionary at http://www.outpost9.com/reference/jargon/jargon_toc.html to define the following hacker terms:
Alpha geek
Grok
Red Book
Wank
Exercise 1.4: Using Security Resources
Using one of the preferred web resources listed in this chapter, find three policy or procedure documents from that resource.
List the documents you selected.
Write a brief essay explaining why those particular documents are important to your organization’s security.
Exercise 1.5: Learning About the Law
Using the Web, journals, books, or other resources, find out if your state or territory has any laws specific to computer security. You might find the following websites helpful:
www.pbs.org/wgbh/pages/frontline/shows/hackers/blame/crimelaws.html
List three laws that you find for your region and provide a brief one- or two-sentence description of each.
Projects
Project 1.1: Learning About a Virus
Using web resources from Appendix A and sites such as www.f-secure.com, find a virus that has been released in the past 6 months.
Research how the virus spread and what damage it caused.
Write a brief (half to one page) paper on this virus. Explain how the virus worked, how it spread, and any other essential information you can find.
Project 1.2: Considering the Law (a Group Project)
Write a description of a computer law that you would like to have passed, along with specifics related to its implementation, enforcement, and justification.
Project 1.3: Recommending Security
Using the Web, journals, or books, locate security recommendations from any reputable source, such as the SANS Institute. Any of the sites mentioned in the “Online Security Resources” section of this chapter would be a good choice.
List five of those recommendations.
Explain why you agree or disagree with each of these five recommendations.