What Is Rootkit? Understanding Rootkit Malware and How to Detect It

A rootkit is a sneaky piece of malicious software that burrows deep into a computer system, allowing cyber attackers to control it from afar without being easily spotted. It can mess with files, processes, and system settings without anyone noticing, so it’s considered one of the most dangerous cybersecurity threats.

Recent studies suggest that around 128 million computers worldwide could be affected by rootkits. Another report shows that nearly 44 percent of rootkit attacks are aimed at government agencies, highlighting their use in high-stakes cyber espionage. These figures show that rootkits are more than random incidents; they’re ongoing threats that can hit individuals, businesses, and critical infrastructure.

Knowing how rootkits operate, spread, and how to get rid of them is essential to staying safe and protecting your privacy. This guide will break down the different types of rootkits, how to detect them, and the best ways to prevent them.

What is Rootkit in Cyber Security?

Rootkits are some of the sneakiest threats in cybersecurity. They hide out while giving attackers deep access to your system. Once a rootkit is on your device, it can steal your data, mess with files, keep tabs on what you’re doing, and even turn off your security software without making a sound. This stealthy behavior lets hackers maintain control over a compromised system for a long time.

The real problem with rootkits is how tricky they are to spot. Unlike regular malware that antivirus programs can usually find and remove, rootkits are made to blend in with the operating system, firmware, or sometimes even the hardware. That’s why they’re popular among skilled hackers and government-backed groups.

These days, rootkits aren’t just about stealing information. They’re also used for spying, committing financial fraud, and creating secret backdoors for attackers to use later on. Since rootkits mix in with normal system processes, someone might never realize their device has been taken over unless they use some specialized detection tools.

How does Rootkit Malware work?

Rootkit malware hides itself deep within a system and gives attackers persistent, stealthy control. Here’s how it typically operates:

1. Initial Infection

Rootkits usually enter through phishing emails, malicious downloads, infected software, or operating system or firmware vulnerabilities. Sometimes they are delivered by other malware, like trojans.

2. Privilege Escalation

Once inside, the rootkit attempts to gain administrative or root-level privileges. This allows it to bypass normal restrictions and modify core system processes.

3. Stealth and Hiding

The defining feature of a rootkit is its ability to remain hidden. It manipulates system files, processes, or kernel functions so that antivirus tools, system monitors, or even the operating system cannot easily detect its presence.

4. Maintaining Persistence

Rootkits embed themselves in critical areas like the kernel, firmware, or boot sector. This ensures they survive reboots and maintain long-term access to the device.

5. Malicious Activity

While hidden, the rootkit enables attackers to:

• Steal sensitive data such as passwords and financial details
• Log keystrokes or spy on activity.
• Open backdoors for other malware
• Disable security protections
• Control the system remotely.

Rootkit Malware vs. Standard Malware

Feature	Rootkit Malware	Standard Malware
Stealth	Operates in hidden mode, often invisible to traditional antivirus tools	Generally visible to antivirus and security scans
Persistence	Can remain active for long periods without detection	Usually detected and removed more quickly
System Access	Often gains deep access to core system files and kernel-level processes	Limited to user-level or application-level access
Primary Goal	Maintain unauthorized access and hide other malicious activity	Execute a specific malicious function like data theft or file corruption
Detection Difficulty	Extremely difficult to detect due to sophisticated hiding techniques	Easier to detect with standard security tools
Removal Complexity	Often requires specialized tools or complete system reinstall	Can often be removed with traditional antivirus or anti-malware software

Types of Rootkits

Rootkits are classified based on where they operate in a system and how deeply they embed themselves. Each type has distinct characteristics that influence how it is detected and removed.

User-mode rootkits

• Operate at the application level with the same privileges as regular programs.
  
• Modify system calls or application behavior to hide files, processes, or registry entries.
  
• Easier to detect than deeper-level rootkits but can still cause disruptions.
  
• It may serve as a gateway for more severe infections.

Kernel-mode rootkits

• Function at the operating system’s core with unrestricted access to hardware and software.
  
• Intercept system functions and disable security tools.
  
• Hide malicious activity from both the user and antivirus programs.
  
• Significantly harder to detect and remove due to deep integration.

Bootloader rootkits

• Also called bootkits.
  
• Target the system’s boot process and load before the operating system starts.
  
• Give attackers control immediately upon powering on the device.
  
• Extremely difficult to detect since they operate before security tools activate.

Firmware rootkits

• It resides in hardware components like BIOS or UEFI firmware.
  
• Survive OS reinstallations and hard drive replacements.
  
• Require firmware reflashing or hardware replacement for removal.
  
• Highly persistent and stealthy.

Hypervisor rootkits

• Create a virtual layer between hardware and the operating system.
  
• Operate beneath the OS, intercepting and manipulating commands.
  
• Remain undetected while controlling all system operations.

File-system rootkits

• Alter file system structures to hide malicious files.
  
• Make files invisible to both the OS and security software.
  
• Can remain undetected for extended periods.

How to Detect and Remove Rootkits

Rootkits are built to avoid detection, making finding and removing them one of the more challenging tasks in cybersecurity. A successful approach combines the right tools, careful observation, and, in some cases, drastic measures.

Recognizing the Signs of a Rootkit Infection

Although rootkits work hard to stay invisible, they can cause subtle system irregularities. Unexpected system crashes, unexplained network activity, missing files, and disabled security software can be early indicators. These signs alone are not proof but signal that further investigation is needed.

Using Rootkit Scanners

Specialized rootkit scan tools are designed to look for hidden processes, altered system files, and suspicious kernel activity that traditional antivirus may miss. Running a scan from outside the operating system, such as from a bootable rescue disk, improves the chances of detection because the rootkit cannot actively hide itself during the scan.

Behavior-Based Detection

Some rootkits avoid signature-based detection by constantly changing their code. Behavior-based detection focuses on identifying unusual patterns, such as processes making unauthorized changes to system files or intercepting data. This method can uncover even unknown rootkit variants.

Manual Inspection for Advanced Users

Experienced security professionals may perform manual system integrity checks, examine kernel modules, verify file hashes, and review registry changes. This is time-consuming but can be effective in identifying sophisticated infections.

Removing Rootkits Safely

Once detected, rootkits can be difficult to remove without damaging the system. Many security tools offer specialized rootkit removal features, but some infections require more drastic action. This can include reinstalling the operating system, restoring from a clean backup, or reflashing or replacing the hardware in the case of firmware infections.

Preventing Reinfection

After removal, closing the security gaps that allowed the rootkit to enter is essential. This includes updating the operating system, applying firmware patches, strengthening access controls, and maintaining regular security scans.

How to Prevent Rootkit Attacks

Preventing rootkit infections requires a proactive approach that reduces vulnerabilities and maintains strong system defenses. Because rootkits rely on stealth and deep access, prevention is often the most effective strategy.

Keep Software and Firmware Updated

• Rootkits often exploit known vulnerabilities in operating systems, applications, or firmware.
  
• Regular security patches and updates help close these vulnerabilities before attackers exploit them.
  
• Updating BIOS or UEFI firmware is especially important since rootkits can embed themselves at this level.

Use Strong Access Controls

• Restrict user privileges to reduce the risk of rootkits gaining administrative access.
  
• Apply the principle of least privilege, granting users and applications only the permissions needed for their tasks.
  
• Limiting unnecessary permissions minimizes opportunities for malicious code installation.

Employ Security Solutions with Rootkit Detection

Modern antivirus and endpoint protection tools often include rootkit scanning capabilities. Using security solutions that detect hidden threats can help catch rootkits early. Running scans regularly, including from bootable rescue environments, improves detection chances.

Enable Secure Boot and Hardware-Based Security Features

Secure Boot prevents unauthorized software from loading during startup and blocks bootloader rootkits from activating. Hardware security features such as Trusted Platform Modules add an extra layer of protection against firmware attacks.

Practice Safe Browsing and Email Habits

• Rootkits commonly spread through phishing emails, malicious downloads, and compromised websites.

• Avoid clicking suspicious links or downloading files from unknown sources.

• Refrain from visiting untrusted websites to lower the risk of infection.

Use a VPN for Enhanced Security

A VPN encrypts your internet connection, protecting your data from interception and reducing exposure to malicious networks. A VPN like AstrillVPN helps shield your device from attacks that exploit unsecured connections. It also adds a layer of privacy, making it harder for attackers to target your system specifically.

Regular Backups and Monitoring

Maintaining regular backups ensures that systems can be restored if compromised. Continuous monitoring of system behavior and network traffic can also detect anomalies that might indicate a rootkit infection.

Real-World Examples & Case Studies

Skidmap: Crypto Mining via Linux Kernel (October 2024)

In late 2024, researchers at Dr.Web uncovered a new variant of Skidmap, a Linux kernel module rootkit designed to hide crypto mining operations on enterprise servers. It exploits misconfigured Redis servers to install itself via cron, disables SELinux, unpacks a rootkit, and deploys a crypto miner with multiple backdoors. These tools conceal CPU and network usage and block loading of detection modules, making this threat especially stealthy and dangerous for corporate environments.

Pumakit: Multi-Stage Linux Rootkit (December 2024)

Elastic Security discovered a highly sophisticated rootkit named Pumakit at the end of 2024. It uses a staged attack architecture in which a cron dropper deploys memory-resident executables, installs a kernel-level rootkit called puma.ko, and loads a userland component known as Kitsune that intercepts system calls. This layered approach allows deep concealment of malicious activity on older Linux kernels.

OVERSTEP: Bootloader Rootkit on SonicWall Devices (July 2025)

In mid-2025, Google’s Threat Intelligence Group identified an OVERSTEP user-mode rootkit deployed against SonicWall SMA appliances. It manipulates the boot process to preserve access, steal credentials, and hide components. Tied to UNC6148, this rootkit has been linked to espionage and ransomware campaigns, with victims’ data leaked as recently as June 2025.

io_uring Exploit: Stealth Rootkits on Linux (April 2025)

Researchers at ARMO demonstrated a proof-of-concept rootkit known as Curing that exploits Linux’s io_uring interface to bypass most security tools. This interface was overlooked by many monitoring systems, creating a serious blind spot. After the discovery, Google disabled io_uring in Android and ChromeOS by default to reduce exploitability.

Conclusion

Rootkits are some of the sneakiest cyber threats because they can hide deep in systems and give hackers long-term access. They can also slip past regular security tools, making them tough to spot and get rid of.

Knowing the different kinds of rootkits can help you understand how they work and what challenges they bring. Each type needs a specific defense strategy, whether it’s user-mode rootkits or those lurking in firmware.

You’ll need specialized scanning tools to find them and look for unusual behavior. Removing a rootkit might mean reinstalling your operating system or updating firmware. The best way to deal with rootkits is to prevent them in the first place by keeping your software updated, using strong access controls, choosing security tools that can detect rootkits, practicing safe browsing, and using VPNs to shield your connections.

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