What Is a Rootkit? Definition, Prevention, and Removal

A rootkit is malicious software (malware) designed to gain unauthorized access to a computer system and maintain control over it while remaining hidden from the user or system administrators. Rootkits often target the lower levels of a computer’s operating system (OS), enabling them to evade detection and manipulate system processes. 

Rootkits have become a significant threat in the cybersecurity landscape, with attackers using them for various purposes, including data theft, system sabotage, and espionage. This article will explore how rootkits work, their dangers, types, examples, and how to prevent and respond to them.

How rootkits work

Rootkits work by exploiting vulnerabilities in a system, often using social engineering tactics or other malware to gain access. 

Once installed, they use a variety of techniques to maintain control of a target system and hide their presence. This may involve replacing or modifying system files, intercepting system calls, and manipulating data within the kernel, the core part of the operating system. 

By operating at such a low level, rootkits can effectively evade detection and control system processes, enabling attackers to execute their malicious objectives.

What are the dangers of rootkit attacks?

Since they’re designed to maintain control over the target system without the knowledge of the system’s users or administrators, the dangers of rootkit attacks are as numerous as they are frightening. They can include data access, system sabotage, remote control, and undetected persistent presence.

Unauthorized access to sensitive information

Arguably the most concerning danger of rootkits, attackers can use rootkits to steal sensitive information which can result in identity theft, fraud, or corporate espionage. 

Examples of data under threat of compromise include:

• Personal data such as names, addresses, phone numbers, social security numbers, and dates of birth, leading to identity theft and fraud.
• Financial information such as credit card numbers, bank account information, and transaction history is also at risk, leading to theft and unauthorized charges.
• Login credentials can also be captured and used to gain unauthorized access to email accounts, social media profiles, or other sensitive online services. Corporate data is also a target and can lead to the compromise of trade secrets, confidential documents, client information, and employee records.
• Intellectual property such as patents, copyrighted material, or proprietary software code can be stolen using rootkits.

Attackers may also use rootkits to intercept, monitor, or manipulate communications such as emails, instant messages, or voice and video calls, leading to eavesdropping or the unauthorized disclosure of sensitive information.

System sabotage

Rootkits can be used to alter system settings, disable security features, or cause system crashes. Considering that rootkits are specifically designed to avoid detection by security software and system administrators, they can be challenging to identify and remove, allowing the attacker to maintain control over the compromised system and execute attacks for an extended period.

Remote control

Attackers can gain full control of a compromised system, using it to launch further attacks, send spam, or host illegal content.

Undetected persistence

Rootkits can remain hidden on a system for extended periods, enabling attackers to maintain control and cause long-term damage. Persistent attacks are a danger associated with rootkits as they include mechanisms that allow them to survive system reboots and reinstallations. This persistence makes it difficult to eradicate rootkits and restore the compromised system to a clean state.

6 types of rootkits

There are several types of rootkits that determine how they invade and infect a system, including kernel-mode, user-mode, bootloader, firmware, memory, and virtualized.

• Kernel-mode rootkits: These rootkits target the kernel and modify core system files or data structures to evade detection and maintain control.
• User-mode rootkits: Also known as application rootkits, these rootkits operate at the user level, often hooking into application processes to intercept and manipulate data.
• Bootloader rootkits: These rootkits infect the bootloader, which is the code responsible for initializing the operating system during startup. They execute before the OS, making them extremely difficult to detect and remove.
• Firmware rootkits: These rootkits target firmware, such as the BIOS or UEFI, enabling them to persist even when an operating system is reinstalled.
• Memory rootkits: Memory rootkits stealthily reside in the random access memory (RAM) of a target machine. Although these rootkits have a brief lifespan due to the volatility of RAM, they can execute extremely harmful activity in the background of a machine.
• Virtualized rootkits: These rootkits create a virtualized environment for the target OS to run in, allowing the attacker to intercept and manipulate data between the hardware and the OS. This makes them extremely stealthy and difficult to detect.

Rootkits prevention best practices

There are a variety of steps to protect your systems from rootkits, including keeping software patched and updated, using strong passwords and multifactor authentication (MFA), using quality antivirus tools, and keeping your employees educated on best practices. 

Although no strategy is guaranteed, the more practices you can put in place, the better your defenses will be.

Keep software up-to-date

Regularly update your OS, applications, and security software to protect against known vulnerabilities that rootkits may exploit.

Use strong passwords and enable multifactor authentication (MFA)

To prevent being compromised by rootkits and other threat actors, always create complex, unique passwords for all your accounts and change them regularly. Avoid using easily guessable information and consider using a reputable password manager.

Additionally, enable MFA for your accounts where available. This adds an additional layer of security, requiring more than just a password to access your accounts.

Install reputable antivirus and antimalware software

Use a trusted antivirus solution to provide real-time protection against rootkits and other threats. Keep the software updated and regularly perform scans to detect and remove any threats.

Be cautious with email attachments and links

Phishing emails often contain malicious links or attachments that can lead to rootkit infections. Always verify the sender’s identity and only open attachments from trusted sources. Make sure you scan attachments for malware before opening them.

Use firewalls

Firewalls can help prevent unauthorized access to your computer or network. Ensure your firewall is properly configured and updated to block potential threats.

Limit user privileges

Avoid using administrator accounts for everyday tasks. Grant users the minimum necessary privileges and use separate accounts for administrative tasks.

Secure your network

Encrypt your Wi-Fi network, change the default router login credentials, and keep router firmware up-to-date. Disable remote management features and, again, use a strong, unique password for your Wi-Fi network.

Be wary of downloads

Only download software from trusted sources and avoid pirated software or cracked applications as they often contain malware, including rootkits.

Educate yourself and others

Stay informed about the latest security threats and best practices. Share this knowledge with friends, family, and coworkers to help create a culture of cybersecurity awareness.

How to detect rootkits

Detecting rootkits can be challenging, as they are designed to remain hidden. However, some methods for detection include using antivirus software with dedicated rootkit scanning abilities or independent rootkit detectors, and monitoring system performance and network connections for anything unusual or suspicious.

• Use antivirus and antimalware software with rootkit scanning capabilities: These rootkit scanning capabilities should implement techniques such as behavioral analysis, integrity checking, signature-based detection, heuristic detection, and boot-time scanning.
• Employ rootkit-specific detection tools: These tools include Malwarebytes Anti-Rootkit Scanner, GMER, Sophos, and more.
• Monitor system performance: Watch for any performance anomalies, such as unexplained slowdowns or crashes.
• Monitor network access: Check for unauthorized network connections or unexpected system processes.

Can you remove rootkits?

Removing rootkits can be difficult due to their ability to hide and resist removal attempts. In some cases, specialized rootkit removal tools or antivirus software may be successful in eliminating the infection. However, in more severe cases, a complete system reinstallation may be necessary to ensure the rootkit has been entirely removed.

Top 3 rootkit removal software

Using a dedicated rootkit removal tool is the best way to remove rootkits from your computer. There are many options available, but three of the best ones are Malwarebytes Anti-Rootkit Scanner, GMER, and RootkitRevealer.

Malwarebytes Anti-Rootkit Scanner

Malwarebytes offers a dedicated anti-rootkit solution for free download, as well as a subscription service called Malwarebytes Premium for more comprehensive, proactive protection at either $44.99 per year for one device or $79.99 per year for three devices. The Anti-Rootkit Scanner scans your files to detect rootkits or other malware, which you can then remove using the same tool.

GMER

GMER is an independent rootkit detector and remover created by a Polish developer in 2004. It has since been integrated with several antivirus software such as Avast, but remains available for free, single download as well. Unfortunately it’s not currently compatible with Windows 11, but it works with Windows NT, 2000, XP, Vista, 7, 8, and 10.

Sophos Rootkit and Bootkit Protection

Sophos is a comprehensive antivirus and antimalware tool that includes rootkit and bootkit detection and removal. You can download its scanner for free, or sign up for Sophos Premium for automatic malware detection and blocking for $44.99 per year.

Popular Rootkit Examples

Stuxnet

Stuxnet is a highly sophisticated rootkit that specifically targeted Iranian nuclear facilities. It’s considered one of the most advanced pieces of malware ever created, as it combined both rootkit and worm capabilities. Stuxnet was designed to infiltrate and sabotage industrial control systems, causing physical damage to the targeted infrastructure.

TDSS/Alureon

TDSS/Alureon represents a family of rootkits responsible for various forms of cybercrime, such as click fraud, data theft, and the distribution of other malware. TDSS/Alureon rootkits are known for their ability to bypass security measures and remain undetected on infected systems. 

This rootkit targets Windows-based systems and is known for its ability to hide its presence from antivirus software and security tools by infecting the system’s Master Boot Record (MBR).

Uroburos

Uroburos, also known as Snake or Turla, is a sophisticated rootkit that mainly targets Windows systems, with a focus on government and high-profile organizations. It’s known for its advanced spying capabilities, including the ability to steal sensitive data, intercept network traffic and take full control of the infected system. Uroburos has been linked to nation-state cyber espionage campaigns.

ZeroAccess

ZeroAccess (also known as Max++ or Sirefef) is a notorious rootkit that targets Windows operating systems. It’s designed to facilitate the distribution of other malware and create large botnets for various illegal activities, including distributed denial-of-service (DDoS) attacks, click fraud, and bitcoin mining. ZeroAccess employs advanced techniques to remain hidden and avoid removal.

Flame

Discovered in 2012, Flame is a highly advanced cyber-espionage toolkit with rootkit capabilities. It is believed to have been used for targeted attacks against organizations in the Middle East and North Africa.

Bottom line: Rootkit risks and removal

Rootkits are stealthy, dangerous, and difficult to detect and remove. They represent a significant threat to personal and organizational security. 

To minimize the risk of rootkit infection, it’s crucial to maintain up-to-date antivirus software, practice safe browsing habits, and be cautious with email attachments and software downloads. Regular system backups can also help mitigate the damage caused by rootkits and other forms of malware. 

In the event of an infection, prompt action and professional assistance may be necessary to fully eradicate the rootkit and restore the affected system.

We reviewed the best antivirus software so you can rest easy with comprehensive antivirus and antimalware protection.