Detecting Hidden System Infection

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Are you familiar with how some malware can hide a system infection? If you’re planning to take the Security+ exam, it’s something you might like to review. For example, can you answer this sample practice test question?

Q. A security administrator recently noticed abnormal activity on a workstation. It is connecting to computers outside the organization’s internal network, using uncommon ports. Using a security toolkit, the administrator discovered the computer is also running several hidden processes. Which of the following choices BEST indicates what the administrator has found?

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 is available at the end of this post.

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 may suspect something is wrong, but antivirus scans and other checks may indicate everything is fine because the rootkit hides its running processes to avoid detection.

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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Detecting System Infection

Detecting Hidden System InfectionIn 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.

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.

The Trojan.Popureb/E rootkit is an example of a rootkit. Among other things, it overwrites the hard drive’s Master Boot Record (MBR), where code is stored to start the operating system. The code on the MBR starts before the operating system boots and it remains invisible to the operating system and security software. Even when antivirus software detects the rootkit, the rootkit protects itself. It prevents any attempts to overwrite the MBR by changing write operations to read operations, though it reports that the write operation completed successfully.

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.

Remember this

Rootkits have system-level or kernel-level access and can modify system files and system access. Rootkits hide their running processes to avoid detection with hooking techniques. Tools that can inspect RAM can discover these hidden hooked processes.


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Q. A security administrator recently noticed abnormal activity on a workstation. It is connecting to computers outside the organization’s internal network, using uncommon ports. Using a security toolkit, the administrator discovered the computer is also running several hidden processes. Which of the following choices BEST indicates what the administrator has found?

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: SY0-401 Study Guide for more information on malware types.

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