This is a blackmail attempt for access to your files. As always, it is best to have your important files backed up on a drive not connected to your PC.
A new version of the CryptoWall ransomware has been released titled CryptoWall 2.0 that includes numerous “enhancements” by the malware developer that resolve issues in the previous version. CryptoWall has been a huge threat for computer users and network administrators since it has been released as it will encrypt all local data and data found on network shares. CryptoWall 2.0 now includes changes that make it better for the malware developer and harder for a victim to recover their files for free. These changes include unique wallet IDs to send ransom payments, secure deletion of original unencrypted files, and the use of their own TOR gateway. These changes are further discussed below…
For more on Cryptowall, Bleepingcomputer has further details: http://www.bleepingcomputer.com/virus-removal/cryptowall-ransomware-information