The CryptoLocker virus is alive and well and now derivatives are propagating the Internet. Without a backup or paying the expensive ransom, in most cases your data would be unrecoverable when attacked. Protect yourself by keeping your anti-virus software and database/definitions up to date and remember to backup your important data regularly. Then test those backups to be certain your backed up data is recoverable.
The cryptolocker and cryptowall file encrypting viruses now demand ransom payment in bitcoins. This further complicates the situation and diminishes the probability of getting your data back without a current backup.