Threat description




Trojan:Android/SLocker.A is reportedly the first Android ransomware that uses file encryption. It is also noted for its use of the TOR anonymizing network to communicate with its controller.


Automatic action

When detected during scanning, F-Secure SAFE will prompt you for a desired action. You may assess the detected file and choose to Uninstall, Quarantine or keep it installed on your device. More information about these options can be found at Help Center: Assess files detected during scanning.

Removal options

Trojan:Android/SLocker disables the Back button when displaying the ransom message to block the user from trying to recover normal use of the device. The user may however have a few seconds to remove the malicious app by pressing the Home button and dragging the app to the top of the screen to uninstall it.

Alternatively, the user may elect to perform a factory data reset on the device to remove the malicious app. This will also erase all user files saved to the device's main memory, but will not affected files stored on an external memory card.

Contact Support

For further assistance, F-Secure customers can request support online via the Request support or the Chat forms on our Home - Global site.

Technical Details

On installation on a device, SLocker scans the device for image, document and video files and encrypts them using the AES encryption algorithm. The malware then displays a ransom message to the user, demanding payment to provide the decryption key necessary to unencrypt the affected files.

Similar to the Trojan:Android/Koler ransomware (which pretends to but does not actually encrypt files on the device), the Back button is disabled when the ransom message is displayed.

SLocker versions

There are currently two versions of SLocker. The most notable version communicates through TOR in order to receive commands. This version is able to collect sensitive information from the device such as its International Mobile Equipment Identity (IMEI) number and return the information to the Command and Control (C&C) server that issues its commands.

The second SLocker version receives commands through SMS messages. Commands have been observed originating from phone numbers traced to Ukraine and Russia.

Both versions of SLocker use the same code (including the same AES password) for decrypting the files held at ransom.

Submit a Sample

Suspect a file or URL was wrongly detected? Send it to our Labs for further analysis

Submit a Sample

Give And Get Advice

Give advice. Get advice. Share the knowledge on our free discussion forum.

More Info