Cryptolocker targets some of the most important files on a PC: things like pictures, documents, movies, music files, etc.

http://searchitchannel.techtarget.com/tip/Cryptolocker-ransomware-protection-A-new-reason-for-old-advice

, according to reports on those who admit to having paid the ransom, less than half say they received a decryption key after payment.

( all quotes)