Network security companies FireEye and Fox-IT have launched a free online tool to help victims impacted by a strain of malware known as Cryptolocker.

The highwayman of the internet, Cryptolocker infects a computer's files before demanding a monetary ransom in exchange for a private key to decrypt them, which is supposedly stored on a secure server.

Despite having infected machines in countries around the world since September 2013, few solutions have been available to assist its victims.

Unlocked

Using the new tool, DecryptCryptolocker, affected users can upload an encrypted Cryptolocker file and receive a private key. Further instructions are then provided on how to apply that key to files encrypted by Cryptolocker to decrypt them.

The companies warn that the tool may not be able to successfully decrypt files in every case as there are multiple variants of Cryptolocker.

According to a blog post on FireEye's website, Cryptolocker, which typically demands around $300 (around £171, or AU$323), was successful in garnering multi-millions in payments during the first two months of distribution.

The malware typically finds itself onto users machines through malicious techniques including spear-phishing emails and watering hole attacks.