A week after a woman from Rochdale was reported to have fallen victim to an encryption Trojan, Arhiveus-A, an older rival has reappeared on the internet.

Kaspersky Lab is reporting that an updated version of GpCode – full name Win32.GpCode.ae in the company’s terminology – is now spreading across Russian websites.

GpCode is reckoned to be the first encryption/blackmail Trojan to have been discovered, after it was traced to Russian websites in the spring of 2005.

In March of this year, another version of the same technique appeared in the form of Cryzip, while last week’s Archiveus.A attack represented a third family.

All work using the same basic technique of archiving and encrypting a user's files, asking for payments or purchases from internet sites in exchange for a password to unlock files. Infection rates tend to be kept to a deliberately low level in order to extend the blackmail window for as long as possible before detection by security companies.

The new version of GpCode swaps RSA 67bit encryption for the harder-to-crack RSA 260bit. As with the original Gpcode, the origin appears to be Russian.

Kaspersky does not specify the passphrase for the Trojan on its website – possibly for competitive reasons – but says it has added an automatic decryption routine that can be used by anyone subscribing to its products.

The company was not immediately available for comment.

This story first appeared on Techworld.com.