Threat description


Category: Malware
Type: Rootkit
Platform: W32


A program (or set of programs) that hides itself by subverting or evading the computer's security mechanisms, then allows remote users to silently control the computer's operating system.


Automatic action

Once detected, the F-Secure security product may either automatically disinfect the suspect file or prompt the user to select a desired action. For more information, see: Support Community article: Automatic actions for viruses also used for suspicious items.

More scanning & removal options

More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.

As hidden items are often related to malware, we ask that you consider sending us a sample of the hidden files to F-Secure Labs via the Submit A Sample (SAS) page for further analysis.

Since the files are hidden, you might not be able to access them directly. To access the files, you might need to do one of the following:

  • Start your computer in safe mode. In safe mode, the files may become visible. To do so, you may need to refer to the relevant Microsoft documentation for your specific operating system version.
  • Rename the files. After renaming the files and restarting the computer, the files may become visible. In some cases, the computer must be started in safe mode after renaming for it to be successful.
  • Reboot your system using Windows Recovery Console. The files should be accessible when using the Recovery Console.

Alternatively, if the hidden files are related to the Master Boot Record (MBR), you may use the following instructions:

Caution: Manual disinfection of the MBR is only advisable for advanced users.

Microsoft provides tools to replace an infected MBR with a copy of the original, clean MBR. To do so:

  • Boot into the Recovery Console.
  • Depending on the operating system in question, run the appropriate command on all infected drives:
    • On Windows XP, run:fixmbr
    • On Windows 7, run:bootrec

Note: For further information on use of the 'fixmbr' command, please refer to the relevant Microsoft documentation.

Technical Details

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 operating system's core components (known as the kernel). In rare cases, the rootkit doesn't need any external files to operate.

Examples of pure rootkits are Hacker Defender and FU. Rootkit-like behavior is also found in other malware types such as backdoors (e.g., Haxdoor, Berbew/Padodor and Feutel/Hupigon).

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).


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