6 Types of Rootkits: Detection, and Prevention Tips

Rootkits are malicious tools cyber attackers use to gain unauthorized access to systems. These persistent and stealthy malware programs embed themselves deep within your operating systems to maintain long-term access to applications, files, and data and avoid detection.

Rootkits are dangerous as they can manipulate system operations, grant attackers privileged access, steal data, and hide malicious code within the compromised systems to regain control. They disrupt your operations, expose sensitive data, damage your brand reputation, and cause non-compliance risks and penalties.

This article covers what a rootkit is, the types of rootkits, best practices to prevent them, and how SentinelOne helps detect and remove rootkits from your systems.

What is a Rootkit?

Rootkits definition says that it’s a malicious program or a set of malware (malicious software) that gives cyber attackers root-level remote access to a computer, device, or software that is not usually allowed to access.

Consisting of usually multiple malware tools, a rootkit is designed to infiltrate systems and allow root access or privileged access to cybercriminals. After gaining unauthorized access to devices, a rootkit hides malicious code in them to be able to control an organization’s devices, operating systems, etc., without getting detected.

As a rootkit can stay hidden for a long period, it’s one of the most difficult malware to discover and eliminate. Some organizations even use rootkits for legitimate use, such as offering end-user support with the knowledge and consent of the end-user.

Most of the rootkits create a backdoor path for malicious software like ransomware, viruses, and other types of viruses to enter an organization’s systems and network for further attack. It contains several malicious tools, including bots, to launch keystroke loggers and DDoS (Distributed Denial-of-Service) attacks. As a result, it can disable security systems, steal credit card details, steal passwords, and other personal details.

The word “rootkit” is a combination of two words — “Root” and “Kit.” The word “Root” defines the admin/privileged account on Unix-like systems, while “Kit” refers to software components executing the tool. Once it’s installed, it gains the ability to execute files, modify system configurations, and do more without being detected.

Why Are Rootkits a Threat?

Rootkits, when used for malicious purposes, are cybersecurity threats that provide unauthorized access to attackers while staying in disguise. This way, they access your systems, networks, operations, and sensitive data, and perform malicious activities, such as stealing data and demanding ransom. Let’s understand the impacts of rootkits:

• Malware deployment: Rootkits deploy malware in your system, such as spyware or ransomware. They create undetectable backdoors for attackers to re-enter your systems even after initial breaches are resolved. The advanced malware can disable traditional security tools, allowing attackers to degrade the system’s performance.
• Difficulty in detection and removal: Rootkits can operate at low levels, such as within the firmware or kernel, and are difficult to detect and remove from your system. Traditional rootkit detection tools usually fail to show if there is a rootkit in your system, making the attacker’s work easier to exploit your systems and data.
• Stealth and persistence: Hackers deploy rootkits deep within a system, such as in the application, firmware, or kernel-level. These can easily bypass security tools like firewalls and traditional antivirus software. Even after reboots or software updates, they are persistent and enable stealth access to your systems.
• Financial and reputational damage: Rootkit attackers can steal or expose your sensitive business and customer data. Failure to meet data security and privacy guidelines brings higher scrutiny from regulators, heavy penalties, and fines. This leads to damaging your finances and reputation in the industry, and you risk losing your customers, partners, and investors.
• Disrupted operations: Organizations want to maintain continuity in their operations to be able to provide good customer service and maintain their trust. Rootkits manipulate and corrupt their files and data, causing system crashes and downtimes. This allows attackers to access critical infrastructure, such as financial systems or supply chains, to disrupt and delay your operations.

6 Types of Rootkits in Cybersecurity

Rootkits enter a system and allow attackers access to all its files and data while remaining hidden from rootkit detection tools. They operate at different levels and are categorized based on their target layer and functionality.

Different types of rootkits in cyber security are:

1. Kernel-Level Rootkits

Kernel-level rootkits are malicious software that operates at the heart of an operating system, known as Kernel. These rootkits modify the operating system kernel to perform harmful activities while hiding their presence. These activities include intercepting network communication, hiding processes, and more. With access to kernel-level privileges, these rootkits are amongst the most difficult malware to detect.

Kernel-level rootkits run in “kernel mode,” which means they contain top-level access to your system resources and allow cybercriminals to manipulate system functions easily. They alter the kernel code to hide their malicious actions from your standard security tools. They function at a similar security level as your operating systems to avoid detection.

How to Detect and Remove Kernel-Level Rootkits?

To detect anomalies in your organization system, you can use kernel integrity tools, such as RKhunter for known and unknown rootkits and Chkrootkit for known rootkits. You can also monitor your systems for suspicious or abnormal behaviors, such as sudden degradation in performance or unexpected crashes. Another option is to compare kernel file and memory system structures to unaltered and known baselines for detecting malware.

Try reinstalling your operating system using a trusted source to remove all malicious modifications and kernel-level rootkits. You can also use specialized tools like advanced security solutions with rootkit removal capabilities.

Kernel-Level Rootkits Examples: Several kernel-mode rootkits known for their distributing ransomware are Necurs, Demodex, Knark, Diamorphine, Glupteba, Reptile, FudModule, Zero Access, and Adore.

2. User-Mode Rootkits

User-mode rootkits are malicious software designed by cybercriminals to operate at the application layer of the computer network. This is why they are also known as the application rootkit. They work within the boundaries of user-level applications and processes by replacing the system libraries and executables and modifying the behavior of APIs.

A user-mode rootkit aims to hide its presence while allowing the cyber attacker to maintain control over your compromised system without detection. Although it is less invasive than kernel-level rootkits, it is a threat due to its ability to manipulate application behavior. It first enters your system and replaces the standard system files to hide its malicious files. The main goal is to intercept API calls to manipulate how your applications work.

How to Detect and Remove?

You can use various techniques and tools to detect and eliminate user-mode rootkits from your system.

• Monitor your system behavior regularly for unusual activities, such as memory usage or high CPU usage by unknown entities, suspicious network connections, and missing files.
• Compare your system files with your original versions to detect malicious changes in your systems.
• Use techniques like API monitoring, rootkit scanners, and memory analysis to detect user-mode rootkits easily.

Once you detect the rootkits, the removal process is not so difficult. Terminate suspicious processes running in your computer using specialized tools like endpoint detection and response (EDR) tools or task managers. You can restore your altered files from backups to run operations smoothly. Use advanced antivirus and cybersecurity software to scan your systems for rootkits.

User-mode rootkit examples: Some popular user-mode rootkits are Hacker Defender, Vanquish, Adore-ng, and Aphex.

3. Bootkits

Bootkits are the kernel-level rootkits that attack volume boot records, Unified Extensible Firmware Interface, master boot records, and boot section before the system loads. They target a computer’s boot process by establishing control over the system early in the boot sequence. They usually enter through a USB drive, external hard drive, or disc, as these processes tell attackers where the bootloader program is.

When cybercriminals find the bootloader program, they replace the genuine bootloader with a malware bootloader. They modify the bootloader and inject malicious code to allow attackers to control the system. Bootkits are hard to detect and can severely damage your systems.

How to Detect and Remove Bootkits?

Detecting and removing bootkits is challenging because they operate at a low level before the operating system loads. However, with advanced tools and techniques, you can easily identify and eliminate them in your system. Monitor your systems continuously to check if your system is slow or showing abnormal behavior. Use endpoint detection tools to identify threats.

The removal process of bootkits might cause certain damages to your system. So, back up your critical files to an external drive or cloud storage and scan them for malware. Utilize a high-end cybersecurity tool to remove bootkits from your bootloader. You can also repair the bootloader using the command prompt or update the firmware to overwrite the malicious code.

Bootkit examples: Some popular bootkits are Stoned Bootkit, Rovnix, Olmasco, TDL4, Mebroot, MoonBounce, GrayFish, FinFisher, and Petya.

4. Memory-Based Rootkits

Memory-based rootkits occupy the system’s RAM and are designed to be volatile and operate in stealth. They can even bypass detection if you use a traditional threat detection tool. The problem with memory-based rootkits is that they don’t leave any traces on the file system to investigate, so, they are often harder to detect and remediate. They can disappear if you reboot your computer, but cause a lot of damage to it when active.

Memory-based rootkits consume plenty of RAM resources through malicious programs to hamper performance and reduce productivity. They modify system functions, kernel structure, and APIs in memory to hide its presence. They use process hollowing, code injection, and DLL injection methods to enter the system’s memory and compromise the running process.

How to Detect and Remove Memory-based Rootkits?

Watch out for unusual system slowdowns, network traffic anomalies, and unexpected memory usage spikes to detect memory-based rootkits. Use advanced cybersecurity tools like kernel debuggers to monitor and identify unauthorized modifications to kernel structures.

Memory-based rootkits are volatile, so you can reboot your system to remove the rootkit. However, you need to secure all your files and data and inspect the root cause of the attack to back up all the information after secure rebooting. If you detect its presence, immediately disconnect the system from the network to prevent further spread of the malware. Always use a secure environment to remediate the system and continue your operations without disruptions.

Memory-based rootkit examples: DarkComet RAT, Duqu, Stuxnet, Fanny Worm, and Code Red are some memory-based rootkits that exploit organizations’ systems.

5. Firmware Rootkits

Firmware rootkits target the devices’ firmware, such as network cards, hard drives, and BIOS. They are persistent malware and can easily survive when you reboot or reinstall your operating system. They use a platform or device to insert a persistent malware image in the network card, BIOS, hard drive, or router and remain hidden for a long time.

Firmware is the low-level software that manages your system functionality and provides an interface between higher-level software and hardware. Firmware rootkits operate at the same level and work at the same interface to steal critical information. This rootkit also has legitimate uses, such as anti-theft technology preinstalled in BIOS images by the third-party vendor. However, cybercriminals use this process to exploit your system data.

How to Detect and Remove Firmware Rootkits?

Firmware rootkits are persistent and stealthy, and reside in a device’s firmware to operate at a low level. You can monitor your system to watch for unexpected system reboots, inability to re-flash the firmware, anomalies during the boot process, and re-infection after system reinstallation. Also, look out for unusual network traffic from firmware-level components, performance issues, etc., to detect firmware rootkits.

Reflash the firmware with a trusted and clean version from the hardware manufacturer and replace your compromised hardware if the rootkit persists after flashing. You can use advanced security tools to detect and remove firmware rootkits without affecting your system’s performance or compromising data.

Firmware rootkit examples: Some of the firmware rootkits are LoJax, MoonBounce, Shamoon, VGA, Cloaker, Thunderstrike, and the hacking team’s UEFI rootkit.

6. Hypervisor (Virtualized) Rootkits

Hypervisor rootkits are advanced malware that cybercriminals use to attack your system’s virtualization technology and gain control. They are also known as virtualized toolkits that target the software layer to exploit virtual machines (VMs). They create a malicious virtual machine in your operating system as a guest to interact and manipulate system operations without detection.

Hypervisor rootkits don’t need to modify or change the kernel of the operating system to bring down the system’s performance. Instead, they install themselves as malicious VMs or modify existing VMs to sit between the OS and hardware. They also gain control over the operating system and modify system behavior to steal sensitive information.

How to Detect and Remove Hypervisor Rootkits?

Due to low-level operation, detecting and removing hypervisor rootkits is complex using traditional security tools and methods. You need to implement advanced cybersecurity solutions to identify and eliminate the rootkit without compromising data and system performance. You can also perform external and internal monitoring to find slower performance issues, abnormal resource usage, and issues in the hypervisor layer.

Get the official hypervisor installation package from a trusted vendor and reinstall it to regain all your secure configurations. You can update hypervisor and firmware software by applying the latest updates to patch vulnerabilities easily. The best way to remove stealthy rootkits is to back up all your data, wipe the complete system that includes firmware and storage drivers, and reinstall the hypervisor and OS in your system to eliminate virtualized rootkits.

Hypervisor rootkit examples: Some of the hypervisor or virtualized rootkits such as Blue Pill, SubVirt, and Vitriol, are used to demonstrate the potential of hypervisor-level attacks.

Preventing Rootkits: Best Practices

Rootkits are the most stealthy and persistent forms of malware that are capable of hiding their presence while allowing attackers to get unauthorized access to systems. For operational continuity and maintaining your company’s reputation, implement the below best practices to prevent rootkits from entering your system’s application, kernel, or firmware layer.

• Keep systems updated: Cyber attackers target outdated firmware or software because they contain vulnerabilities that are easy to exploit. You must regularly update your operating systems, firmware, and applications to patch known and unknown vulnerabilities. Implement automation to reduce delays and secure your application and firmware layer.

• Improve authentication mechanisms: Compromised and weak credentials allow attackers to install rootkits remotely. So, you must strengthen your authentication mechanisms by implementing multi-factor authentication for everyone, executing a strong password policy, and monitoring suspicious login attempts.

• Implement Least Privilege Access: Excessive access permissions increase your attack surface and pave the way for rootkits to enter the system. Limiting user privileges can reduce the chances of gaining administrative access and minimize the attack surface. Assign users only the necessary permissions to fulfill their job roles and restrict admin privileges. Always look out for unauthorized access, investigate the incident, and prevent rootkits from entering.
• Use advanced threat detection solutions: Rootkits are designed to elude traditional security tools and antivirus software. Use advanced cyber security solutions like SentinelOne to detect and eliminate rootkits. Use endpoint detection and response tools, such as SentinelOne Singularity™ XDR, to monitor and analyze endpoint activities 24/7.
• Secure the boot process: Rootkits target the bootloader to gain access to your system boot program when the system starts. You can use Unified Extensible Firmware Interface (UEFI) instead of BIOS to improve boot security. Configure your systems to boot from trusted sources to reduce cyber attacks.
• Regular backups: When you try to eliminate rootkits from your system, it could affect your system files and data, such as deleting important information. So, always back up your sensitive data so you can restore it after remediating the rootkits. You may also want to backup your data offline, as it is more secure from cyber threats.

How can SentinelOne help?

Rootkits are dangerous, but SentinelOne’s Singularity Platform is built to detect and respond to them with advanced AI capabilities. It’s an AI-based extended detection and response (XDR) platform that offers complete visibility into your systems, detects rootkits and threats accurately, and offers automated responses to speed up remediation.

• Greater visibility: The platform allows you to visualize all your endpoints, network components, Kubernetes clusters, servers, VMs, containers, and other assets stored in on-premise, private, and public data centers.
• Real-time threat detection: SentinelOne’s XDR continuously monitors your systems for abnormal or suspicious behavior that could indicate a threat. It uses AI and ML algorithms and behavior analysis to detect rootkits and other advanced cyber threats, such as ransomware, fileless malware, spyware, etc., in real-time.
• Automated response: The Singularity Platform offers automated responses to rootkits to speed up the remediation process and protect your organizational assets. Once it identifies rootkits, it immediately isolates the compromised system, removes the malware, and restores the system automatically. The platform also alerts your security team, so they can investigate the incident in detail.

Take a product tour to explore the Singularity Platform by SentinelOne.

Conclusion

Rootkits use stealth and deep system integration to harm the system’s operations and security and avoid detection. They operate at various levels, such as kernel space, user space, firmware, bootloader, and virtual machines, to maintain long-term control and hide malicious code.

Knowing the types of rootkits and how they operate helps you develop solid defense strategies against them. To detect rootkits, you need a combination of advanced cybersecurity tools, continuous monitoring, and the use of least privilege access. Plus, prioritize security best practices, including system integrity checks, employee awareness, and regular updates to keep your systems safe.

FAQs

1. What is a Rootkit in Cyber Security?

A rootkit is a type of malware that enters your system and gains access to your applications, operations, and data without being detected. It is a collection of malicious tools that let cyber criminals gain root-level access to the operating system and perform malicious activities. It is used to steal passwords, credit card information, and other sensitive data. Rootkits can also disable security tools, launch DDoS attacks, delete OS code, and intercept user’s personal information.

2. What are the Main Types of Rootkits?

There are six types of rootkits based on the level at which they operate within the system:

• Kernel-level rootkits
• User-mode rootkits
• Bootkits
• Memory-based rootkits
• Firmware rootkits
• Hypervisor (virtual rootkits)

Each type implements unique operations and affects different corners of the system’s operations. There are specialized tools to remove rootkits from the systems effectively.

3. What is the most dangerous Type of Rootkit?

The most dangerous type of rootkit is kernel-level rootkit. It can integrate with your operating system so deeply that no traditional methods or antivirus software can remove it from the system. They have top-level access to alter the kernel mode and grant unrestricted access to system resources. It allows attackers to manipulate the files, system calls, and processes without detection.

4. How are Rootkits Installed on a System?

Rootkits are installed on a system using various techniques and methods. Some of them are email phishing campaigns, crafted malicious PDF files, executable malicious files, Trojan horse programs, network attacks, supply chain compromises, infected USB drives, and fake software. These methods rely on user deception or exploiting security vulnerabilities within the system.

5. How are Rootkits Removed?

Rootkits can be removed using several methods. Since they are persistent and work in stealth, you need advanced cybersecurity tools to detect and eliminate rootkits from the root. You can scan using advanced antivirus software or XDR solutions to detect rootkits. If the rootkit is deeply embedded, you can remove it by reinstalling or rebooting the whole operating system. Use a professional repair solution if the rootkit exploits your BIOS.

6. How can I Detect Rootkits on my System?

You can detect rootkits on your system using advanced cybersecurity tools, running boot-time scans, verifying system integrity, checking logs, reinstalling OS, analyzing network traffic, and inspecting processes. You can monitor unusual crashes, slow system performance, and unauthorized access to detect rootkits easily.

7. What are some Real-World Examples of Rootkits?

There are many cases where rootkits have infected millions of computer systems worldwide. Some rootkits examples are ZeroAccess rootkit, Duqu, TDL-4, Lojax, Rovnix, Sony BMG, Stuxnet, Flame, Equation Group, Hacking Team, and Necurs botnet rootkit. Due to these rootkits, many companies have faced lawsuits and backlash, and were forced to pay penalties for failing to comply with regulatory standards.

8. How can I Protect my System from Rootkits?

To protect your systems from rootkits:

• Always keep your software, applications, devices, and operating systems updated and patched.
• Monitor your systems continuously for suspicious activities.
• Never download software from unreliable sources.
• Avoid clicking on suspicious links or downloading attachments in emails.
• Use anti-malware solutions that can protect against rootkits.
• Use advanced solutions like XDR.