Virus hunters have discovered a new Trojan that encrypts files on an infected computer and then demands $300 in ransom for a decryption password. The Trojan, identified as Cryzip, uses a commercial zip library to store the victim’s documents inside a password-protected zip file and leaves step-by-step instructions on how to pay the ransom to retrieve the files. It is not yet clear how the Trojan is being distributed, but security researchers say it was part of a small email spam run that successfully evaded anti-virus scanners by staying below the radar.