Trojan:Boot/mebroot, Trojan:Boot/mebroot.b


Rootkit:Boot/Mebroot is a sophisticated program capable of replacing and controlling the infected system's Master Boot Record (MBR), then downloading and installing additional malware onto the infected system.

Windows: MBR Repair

Windows includes 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.

Suspect a file is incorrectly detected (a False Positive)?

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 detection database 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.

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Submit a sample

Submit a file or URL for further analysis.

Technical Details

The MBR is the first physical sector of a computer system's hard drive and contains the first code loaded and executed from the drive during the boot process. A malicious program capable of subverting this critical sector is therefore able to control the entire system, while masking its own presence from the user.

The technical features of the Mebroot rootkit are discussed in further detail in the following Labs Weblog posts:


Mebroot is known to be distributed either by a trojan-downloader program found on malicious websites, or via an exploit.


Once installed, Mebroot silently downloads further programs onto the infected system; the downloaded malware appear to target online banking and other financial systems.