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Aliases :

Rootkit:W32/Whistler, Rootkit.MBR.Whistler.A, Rootkit.MBR.Whistler.B, rootkit.mbr.whistler.a (boot image), Rootkit.mbr.whistler.b_(boot_image)


Rootkit:W32/Whistler infects the computer system's Master Boot Record (MBR) and loads additional malicious files while the system is starting up (booting).


Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

Sending a sample to F-Secure Labs

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:

  1. 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.
  2. 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.
  3. 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:

Manual repair of the Master Boot Record (MBR)

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.

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note: You need administrative rights to change the settings.

Technical Details

F-Secure products may detect the rootkit file itself using the detection names Rootkit.MBR.Whistler.A (boot image) or Rootkit.MBR.Whistler.B (boot image).

As with most rootkits, Whistler is used to help other malicious programs to silently launch themselves on an infected computer. The additional files loaded by the rootkit are stored in the raw disk sectors and are therefore not visible in the file system. These files, which are typically malware, may also be identified by detections such as Gen:Variant.Unruy.4.