A rootkit is usually a standalone software component that attempts to hide processes,files, registry data and network connections. Though rootkits are not malicious in themselves, numerous malware use a rootkit component to facilitate their malicious routines and to protect the malware from detection/deletion.
A rootkit can be either user-mode or kernel-mode. A user-mode rootkit is usually dropped as a DLL file, which the malware then loads to all running processes in order for the rootkit to run; a kernel-mode rootkit is usually dropped as a driver file, which is then loaded as part of the kernel, or the operating system's core components. In rare cases, the rootkit doesn't need any external files to operate.
Examples of pure rootkits are Hacker Defender and FU. Some spyware and adware programs (e.g., EliteToolbar, ProAgent and Probot SE) also use rootkit techiques, as well as some trojans (e.g., Haxdoor, Berbew/Padodor and Feutel/Hupigon), and worms.
Hidden Items or Processes
Hidden processes, files and applications detected on the system are displayed as suspicious items. The presence of these items can indicate the following:
- A normal, non-malicious application might be hidden for some reason OR
- Malware (a stealth virus, rootkit or spyware) may be hiding on the computer
There are many malicious and non-malicious reasons why items can be hidden on the computer:
XCP Digital Rights Management (DRM) software: The copy-protection software included on some music CD's hides files and processes. While the files are not malicious, there are security risks involved with them.
Backdoor:W32/Haxdoor: Note that this backdoor hides important system files, which are not malicious themselves.
Apropos: This is a family of spyware that hides files and processes.
MBR Rootkit (boot image)
A detection name that uses the format "Rootkit.mbr.[variant] (boot image)" indicates the possible presence of a hidden component or program that affects the Master Boot Record (MBR), a dedicated area of a storage device - such as a hard drive or a floppy disk - that contains critical information for starting the main operating system (OS).