Category :


Type :


Aliases :

Cryptolocker, Trojan.cryptolocker, Trojan.downloader.cryptolocker


Cryptolocker encrypts files on the compromised computer and demands a ransom to provide the decryption key needed to decrypt the files.


F-Secure detects Cryptolocker malware using a variety of generic detections. Once detected, the F-Secure security product will automatically remove the file.

Restore from backup

Like most ransomware, though the malware itself can be removed, the encryption used to take the files hostage is sufficient to make it very difficult to decrypt the files without the necessary decryption key.

In such circumstances, the recommended course of action is to report the crime to the relevant authorities and restore the affected data from a backup.

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

Cryptolocker is ransomware that is spread by both malicious file attachments to email messages and via the Gameover Zeus botnet. When Cryptolocker is run, it encrypts files on the compromised machine and displays a message informing the user that a decryption key must be purchased in order to recover access to the files held at ransom.

For more information, see:

Further analysis

If you believe you have encountered an undetected Cryptolocker sample, please send it to us for analysis via our Submit A Sample (SAS) page.


Update: 10 February, 2015: Details of the CTB-Locker ransomware which were originally posted in this description have now been moved to a separate description, Trojan:W32/CTB-Locker, to minimize confusion between these two ransomware families.