In cyber security, the threats of rootkits are hazardous. These could be advanced malware programs designed to act stealthily and grant administrative privileges to the attacker at the system level. Cybercriminals use rootkits to gain remote access to valuable data and system settings, often remaining undetected for quite a long time. Understanding what rootkits are, their types, infection methods, and ways of defense are critical to protecting your systems.

A rootkit is malware that hides itself or other software from the system, typically to grant unauthorized access to a system. The term “rootkit” itself is derived from “root,” meaning the highest order in a system, and “kit,” meaning a collection of tools. Very rarely do they infect just one layer of a system; this is one of the reasons it is tough to spot and remove a rootkit. Once installed, they can be used by attackers to snoop through user activities, steal sensitive data, install more malware, or turn off security measures.

There are rootkits classified according to where they embed themselves. Here is the breakdown of basic types:

• Application rootkits Infect software applications to change their behavior or steal information without altering the lower levels of the system.
• Kernel rootkits: A direct attack against the kernel as the heart of the operating system, modifying its code and data structures. Such rootkits are hard to detect.
• Bootloader rootkits infect the system’s bootloader. The malicious code executes before loading the real operating system, making detection difficult.
• Hardware and firmware rootkits: These types of rootkits exploit vulnerabilities in hardware components, such as network cards, hard drives, or firmware, to create persistent threats. 
• Virtualized rootkits: The attackers create a virtualized environment below the operating system. Here, they can also monitor and control the system at a close level while remaining invisible. 
• Memory rootkits: These rootkits merely reside in RAM. Since traditional storage-based scanning cannot detect these processes, memory rootkits will evaporate upon reboot.
• Username rootkits:  These rootkits change usernames and authentication credentials and masquerade themselves as some other bona fide user entity to go unrecognized.

Some of the most notorious cyberattacks in history include rootkits. 

Sony BMG Rootkit Scandal, 2005: Sony secretly installed rootkits onto CDs to prevent users from making copies. The opened vulnerabilities in users’ computers made the event very controversial, and associated lawsuits followed.

Stuxnet (2010): This became well-known as the cyber weapon applied in the infringement, often referred to as an attempt to sabotage Iran’s nuclear program. It used a rootkit to hide itself and its activities from being detected by antivirus tools and security systems.

Rootkits can infect systems by a variety of means, including the following:

• Phishing Emails: Attackers send phishing emails with attachments or a link to a rootkit that can be downloaded by clicking the link.
• Drive-by Downloads: Sometimes, simply visiting malicious Web sites can automatically download rootkits—there’s no need for user interaction.
• Trojan Horse Malware: Most of the time, rootkits are integrated into other different software, either legitimate ones that users download or install without their knowledge, carrying the hidden threat within.
• Exploiting vulnerabilities: Attackers can use the not-upgraded vulnerabilities of the operating system or applications to install rootkits into these systems.
• Supply Chain Attacks: Hardware or firmware rootkits can be installed in the devices in advance.

It is rather challenging to detect rootkits because of their stealthy nature; nevertheless, there are several methods and tools for this:

• Behavioral analysis: This checks for atypical system behaviors, such as sudden performance drops, unexplained crashes, or unusual network traffic.
• Detection Signature-based: It detects rootkits using the databases mentioned above, which consist of the rootkits’ signatures. Examples include using rootkit-scanning antivirus applications.
• Integrity Checkers: The system’s integrity checkers compare system files and directories with their trusted and known clean states to detect unauthorized tampering or changes.
• Memory Scanning: Another reason is that some rootkits reside in RAM only; some dedicated tools, like GMER, can be used to scan memory for suspicious activity.
• Rootkit Remover Tools: Tools like Malwarebytes, Anti-Rootkit and Sophos Rootkit Scanner are designed to detect and remove hidden rootkits.
• Manual Forensic Analysis: In very extreme cases, to detect deeply embedded rootkits, forensic analysts manually scrutinize a system’s code, kernel modules, and boot sectors.

Some of the measures to prevent the attacks of rootkits are as follows:

• Update Regularly: Keep updating the operating systems, drivers, and applications to versions that will prevent vulnerabilities from being exploited by any rootkits.
• Use Antivirus/Anti-Rootkit Tools: Run popular antivirus solutions that offer rootkit detection and scan explicitly for rootkits periodically.
• Enable Secure Boot: This will allow hardware that supports Secure Boot mechanisms to ensure the integrity of the boot loader against the execution of any unauthorized code during system boot-up.
• Least Privilege Principles: This limits administrative privileges, hence the possibility of installation of a rootkit due to unauthorized access.
• Intrusion Detection Systems: IDS tools can monitor network traffic and system behavior in search of possible rootkit activities.
• Network Segmentation: Segment the network to contain the malware infection in case of an attack from other rootkits and malware.
• Staff Education: Educate employees about phishing attacks and how not to download unverified software.

Since rootkits can easily hide themselves and offer an attacker complete control over the infected system, they are extremely dangerous to cyber security. Knowing the various types of rootkits, propagation techniques, and methods of detection and prevention enables organizations and individuals to improve the security level of their systems. Security processes, monitoring of systems, and state-of-the-art anti-rootkit solutions are among the ways of mitigating the dangers related to rootkits.