Malware strain of malware called CryptoLocker is a prolific strain that uses strong encryption to lock files that are likely to be the most valued by victim users. Victims are given 72 hours to pay the ransom typically a few hundred dollars worth of Bitcoins after which time the ransom demand increases fivefold or more. Two security firms Milpitas, Calf. based FireEye and Fox-IT in the Netherlands launched decryptcryptolocker.com, a free online service that can help victims unlock and recover files scrambled by the malware.”]
Source: https://krebsonsecurity.com/2014/08/new-site-recovers-files-locked-by-cryptolocker-ransomware/