January

CryptoLocker, the Bitcoin demanding ransomware menace, has infected as many as a quarter of a million machines since it first surfaced last September, according to research from Dell SecureWorks; Counter Threat Unit.
Earlier versions of CryptoLocker typically arrived in email as an executable file disguised as a PDF, packed into a .zip attachment. A spam run targeting millions of UK consumers prompted a warning from the UK National Crime Agency back in November. Only Windows machines can be infected by the malware.
If it successfully executes, CryptoLocker encrypts the contents of a hard drive and any connected LAN drives before demanding payment of up to 2 Bitcoins (payable within 72 hours) for a private key needed to decrypt the data. The malware uses a well-designed combination of 256-bit AES and 2048-bit RSA crypto that mean that without backups victims have little choice but to pay up if they ever want to see their data again.