New Directions in Malware
Kaspersky Labs reports on extortion scams using malware:
We’ve reported more than once on cases where remote malicious users have moved away from the stealth use of infected computers (stealing data from them, using them as part of zombie networks etc) to direct blackmail, demanding payment from victims. At the moment, this method is used in two main ways: encrypting user data and corrupting system information.
Users quickly understand that something has happened to their data. They are then told that they should send a specific sum to an e-payment account maintained by the remote malicious user, whether it be EGold, Webmoney or whatever. The ransom demanded varies significantly depending on the amount of money available to the victim. We know of cases where the malicious users have demanded $50, and of cases where they have demanded more than $2,000. The first such blackmail case was in 1989, and now this method is again gaining in popularity.
In 2005, the most striking examples of this type of cybercrime were carried out using the Trojans GpCode and Krotten. The first of these encrypts user data; the second restricts itself to making a number of modifications to the victim machine’s system registry, causing it to cease functioning.
Among other worms, the article discusses the GpCode.ac worm, which encrypts data using 56-bit RSA (no, that’s not a typo). The whole article is interesting reading.