What is a Rootkit?

A rootkit is a type of malicious software (malware) designed to gain unauthorized access to a computer system and hide its presence or the presence of other malware.

Characteristics of a rootkit are as follows:

  1. Stealthy: Rootkits operate at a low level in the system (kernel or firmware) and are very difficult to detect.

  2. Persistent: They often survive reboots and can re-install themselves if removed incorrectly.

  3. Backdoor Access: Rootkits commonly provide attackers with administrative control (root access) over the target system.

Types of rootkits

  1. User-mode Rootkits: Operate at the application level. Easier to detect and remove.

  2. Kernel-mode Rootkits: Operate at the operating system level. More powerful and harder to detect.

  3. Bootkits: Infect the master boot record (MBR) or UEFI firmware, loading before the OS.

  4. Firmware Rootkits: Infiltrate device firmware like network cards or BIOS, making them extremely hard to detect.

  5. Virtual Rootkits: Create a virtual machine layer to monitor and manipulate the real OS undetected.

Common Uses:

  • Hiding other malware (e.g., keyloggers, trojans).

  • Maintaining long-term access to a system.

  • Stealing data or credentials.

  • Bypassing security software.

DETECTION AND REMOVAL

here are ways to tell if you have been infected with a rootkit on your computer or your device. Here are some ways to tell and how to remove them.

Behavioral Signs

  • Sluggish system performance.

  • Disabled antivirus or firewall.

  • Strange network activity or unknown processes.

  • Files or programs "disappearing."

Rootkit Scanners & Tools

  • Windows:

    • Microsoft Defender Offline (Boot-time scan).

    • GMER – Scans for hidden processes and modules.

    • TDSSKiller (from Kaspersky) – Detects and removes bootkits/rootkits like TDSS.

  • Linux:

    • chkrootkit – CLI tool for Unix/Linux systems.

    • rkhunter – Scans for known rootkits, backdoors, and exploits.

Offline Scanning

  • Boot from a trusted external OS (like a Live Linux USB) to scan the drive without the rootkit running.

Removal Process

  • Automated Tools

    Run tools like TDSSKiller, Malwarebytes Anti-Rootkit, or Sophos Rootkit Removal Tool.

    • For Linux, use rkhunter --remove or manual cleanup based on logs.

  • Boot-Time Antivirus Scan

    • Use tools that scan before the OS loads (e.g., Microsoft Defender Offline, Bitdefender Rescue CD).

  • Manual Removal (Advanced Users)

    • Requires advanced knowledge of the OS.

    • Involves analyzing and removing suspicious drivers, processes, or registry entries.

    • Dangerous: Mistakes can crash the system.

  • Best Option for Deep Infections

    • Wipe and Reinstall the operating system.

    • If it's a bootkit or firmware rootkit, consider:

      • Reflashing the BIOS/UEFI firmware.

      • Replacing the hard drive or affected hardware.