Original URL: http://www.theregister.co.uk/2006/07/24/ransomware/

Ransomware getting harder to break

The evolution of an 'uncrackable' threat

By John Leyden

Posted in Security, 24th July 2006 20:08 GMT

Hackers may soon be pushing out ransomware packages so complex that they're beyond the decryption capabilities of the anti-virus industry, according to a study by Russian anti-virus firm Kaspersky Lab.

The report, Malware Evolution: April – June 2006, Hidden Wars, states that the creators of so-called ransomware packages are making the lives of security researchers more difficult by using more powerful and sophisticated encryption algorithms. Ransomware packages use malicious code to gain control of user files, encrypt them and threaten users that they won't see these files again unless they hand over a cash "ransom" to hackers.

Examples of ransomware malware, which made its first appearance only months ago, include Gpcode, Cryzip, and Krotten. At first the encryption approaches taken by hackers were crude. But Gpcode-AC, first detected in January 2006, used the RSA algorithm to create a 56-bit key. Since then, the unknown author of the virus has produced variants that use more complex encryption keys. The last detected variant Gpcode-AG uses a 660-bit key.

"We were able to decrypt 330 and 660-bit keys within a reasonably short space of time, but a new variant, with a longer key, could appear at any time. If RSA, or any other similar algorithm which uses a public key, were to be used in a new virus, anti-virus companies might find themselves powerless, even if maximum computing power was applied to decrypting the key," warns Aleks Gostev, senior virus analyst, Kaspersky Lab.

Kaspersky Lab warns that even if the original authors of ransomware families are tracked down there's nothing to prevent other hackers from developing the technique. Security firms might succeed in developing approaches that make it impossible for malicious users to encrypt or archive users' data. But users have the power to render ransomware attacks impotent by regularly backing up documents and email databases, a sensible security precaution that's all too infrequently applied. ®