Discovering Infected Systems

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If you’re planning to take the SY0-501 version of the Security+ exam, you should understand different malware types. Attackers install these onto systems using a variety of devious means. Infected systems give various symptoms, such as running slower, starting unknown processes, sending out email without user action, rebooting randomly, and more.

For example, can you answer this question?

Q. A security administrator recently noticed abnormal activity on a workstation. It is connecting to systems outside the organization’s internal network using uncommon ports. The administrator discovered the computer is also running several hidden processes. Which of the following choices BEST describes this activity?

A. Rootkit

B. Backdoor

C. Spam

D. Trojan

More, do you know why the correct answer is correct and the incorrect answers are incorrect? The answer and explanation are available at the end of this post.

Organizations need to understand and protect themselves from many different types of threat actors, so it’s valuable to know a little about them, their attributes, and the types of attacks they are likely to launch. This post compares bots and botnets, and rootkits.

Bots and Botnets

Generically, bots are software robots. For example, Google uses bots as search engine spiders to crawl through the Internet looking for web pages. However, attackers also use bots for malicious purposes. A botnet combines the words robot and network. It includes multiple computers that act as software robots (bots) and function together in a network (such as the Internet), often for malicious purposes. The bots in a botnet are often called zombies and they will do the bidding of whoever controls the botnet.

Bot herders are criminals who manage botnets. They attempt to infect as many computers as possible and control them through one or more servers running command-and-control software. The infected computers periodically check in with the command-and-control servers, receive direction, and then go to work. The user is often unaware of the activity.

Most computers join a botnet through malware infection. For example, a user could download pirated software with a Trojan or click a malicious link, resulting in a drive-by download. The malware then joins the system to a botnet.

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Bot herders have been using Mirai to create large botnets. Mirai infects Linux systems that are running out-of-date versions of Linux and join them to a botnet. This includes Linux software running on Internet of things (IoT) devices such as digital cameras connected to the Internet. Infected devices search for other IoT devices on the Internet and infect them. Attackers have published the source code for Mirai in public forums, making it easily accessible by many attackers.

A Mirai botnet launched an attack in October 2016 against Domain Name System (DNS) servers. It included about 100,000 simple devices such as digital cameras and printers that were connected to the Internet. The bot herders directed the devices to repeatedly query DNS servers in a protracted distributed denial-of-service (DDoS) attack. This attack overwhelmed the DNS servers and prevented users in the United States and Europe from accessing many common web sites, such as Amazon, Second Life, Twitter, CNN, BBC, Fox News, Tumblr, Reddit, and many more.

Similarly, Wordfence discovered attacks coming from a botnet of approximately 10,000 separate IP addresses in April 2017. After investigating the attacks, they learned that the attacking systems were typically home routers that had a known vulnerability, named the Misfortune Cookie by Checkpoint Software Technologies. Interestingly, Checkpoint reported the vulnerability in 2005. However, this attack showed that a specific Internet Service Provider (ISP) in Algeria was issuing these unpatched routers to its customers.

Botnet herders sometimes maintain complete control over their botnets. Other times, they rent access out to others to use as desired. Some of the instructions sent by the command-and- control servers include:
• Send spam.
• Launch a distributed denial-of-service attack.
• Download additional malware, adware, or spyware such as keyloggers.

Rootkits

A rootkit is a group of programs (or, in rare instances, a single program) that hides the fact that the system has been infected or compromised by malicious code. A user might suspect something is wrong, but antivirus scans and other checks indicate everything is fine because the rootkit hides its running processes to avoid detection.

In addition to modifying the internal operating system processes, rootkits often modify system files such as the Registry. In some cases, the rootkit modifies system access, such as removing users’ administrative access.

Rootkits have system-level access to systems. This is sometimes called root-level access, or kernel-level access, indicating that they have the same level of access as the operating system. Rootkits use hooked processes, or hooking techniques, to intercept calls to the operating system. In this context, hooking refers to intercepting system-level function calls, events, or messages. The rootkit installs the hooks into memory and uses them to control the system’s behavior.

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Antivirus software often makes calls to the operating system that could detect malware, but the rootkit prevents the antivirus software from making these calls. This is why antivirus software will sometimes report everything is OK, even if the system is infected with a rootkit. However, antivirus software can often detect the hooked processes by examining the contents of the system’s random access memory (RAM).

Another method used to detect rootkits is to boot into safe mode, or have the system scanned before it boots, but this isn’t always successful. It’s important to remember that rootkits are very difficult to detect because they can hide so much of their activity. A clean bill of health by a malware scanner may not be valid.

It’s important to remember that behind any type of malware, you’ll likely find an attacker involved in criminal activity. Attackers who have successfully installed a rootkit on a user’s system might log on to the user’s computer remotely, using a backdoor installed by the rootkit. Similarly, attackers might direct the computer to connect to computers on the Internet and send data. Data can include anything collected from a keylogger, collected passwords, or specific files or file types stored on the user’s computer.


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Q. A security administrator recently noticed abnormal activity on a workstation. It is connecting to systems outside the organization’s internal network using uncommon ports. The administrator discovered the computer is also running several hidden processes. Which of the following choices BEST describes this activity?

A. Rootkit

B. Backdoor

C. Spam

D. Trojan

Answer is A. A rootkit typically runs processes that are hidden and it also attempts to connect to computers via the Internet.

Although an attacker might have used a backdoor to gain access to the user’s computer and install the rootkit, backdoors don’t run hidden processes.

Spam is unwanted email and is unrelated to this question.

A Trojan is malware that looks like it’s beneficial, but is malicious.

See Chapter 6 of the CompTIA Security+: Get Certified Get Ahead: SY0-501 Study Guide for more information on malware types.

Check out the Determining Malware Types blog post to know more about other types of malware.

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