Ransomware Race (Part 1): CryptoWall ups the ante

This summer has included the appearance of two strong new malware families onto the file encrypting Windows ransomware market: CryptoWall and CTB-Locker. Of these, CTB-Locker has been the more advanced family, with its use of elliptic curve cryptography for file encryption and Tor for communication with the command & control server. CryptoWall, meanwhile, has used the more traditional combination of RSA and AES for file encryption and HTTP for C&C communication.

more here..............http://www.f-secure.com/weblog/archives/00002729.html