A Trojan making the rounds encrypts victims' files and demands a $300 payment to have them decrypted and unlocked, according to a report by security firm Lurhq Threat Intelligence Group. This so-called "ransomware" Trojan, dubbed Cryzip, is the second of its type to emerge in the past 10 months, following the PGPcoder Trojan. It also is the third such Trojan to appear since 1989.

"Last year, we saw the PGPcoder, and anything that shows itself to be a viable way to make money, usually people start jumping on the bandwagon after that," said Joe Stewart, senior security researcher for Lurhq. The Cryzip Trojan will search for files, such as source code or database files, on infected systems. It then uses a commercial zip library to store the encrypted files. Security researchers, however, have yet to determine how the Trojan is distributed, noting it could come from a number of sources, including malicious Web sites, or enter through a previously created backdoor on a virus-infested computer.