Original URL: http://www.theregister.co.uk/2008/06/06/ransomeware_call_to_arms/

Security militia sought to brutalize ransomware virus

Time to crack some key

By Dan Goodin

Posted in Security, 6th June 2008 22:37 GMT

After discovering a new and improved virus that encrypts important files on infected machines, researchers from Kaspersky are calling on fellow security professionals to lend a hand in cracking the massive key needed to liberate the ensnared data.

The call to arms posted Friday comes two days after the antivirus provider detected a new variant of a malicious file-encryptor dubbed Gpcode. It surreptitiously encrypts a variety of files, including photos and those used by MS Word and Excel and Adobe Reader. Victims can only recover the missing booty by paying a ransom to the miscreants.

When Gpcode first made the rounds two years ago, Kaspersky was able to neutralize the threat by deducing the private key needed to unlock the encrypted data. That was possible because the crooks used a 660-bit RSA key and made some critical mistakes when implementing the encryption algorithm.

Cryptographers won't have as easy a task this time around. Gpcode uses a 1024-bit key and the algorithm seems to be sound, so brute-forcing the scheme will require about 15 million modern computers, and even then, it could take about a year.

"Of course, we don't have that type of computing power at our disposal," Kaspersky says in its appeal. "This is a case where we need to work together and apply all our collective knowledge and resources to the problem."

They've included two public keys - one used to encrypt files on XP and Vista machines and the other for all other versions of Windows. And they've also provided the exponent for the keys. They're especially interested in someone stepping forward with a custom-built application that can tackle the tough job of factoring the key. A forum for the project is here. ®