I know this maybe old news for some of you, however, I just got the chance of reading this great article on Security Focus (it’s been 2 weeks since I add it to my Favorites)

This two part article discusses some good points of Cryptology, more precisely in the field of Cryptovirology.

Writing a virus is just like writing any other piece of software, unfortunately. The designer tries to put some cleverness in the application to improve its function (or stealth), its robustness, its replication strategies, or even its payload. However, when an anti-virus analyst gets ahold of such a piece of code, he learns how it works, what it does, and so on. In the end, both the writer and the analyst share the same view of the virus, in what amounts to a Turing machine (we have a state-transition table and a starting state).

You read about the WoW Trojan and the Trojan Writers Coding for Money here at Darknet. This article will give you a clear idea of how things work.

To open your appetite, let me give you a little excerpt from the article:

A basic model seen today

This basic model can be seen according to intended targets:

• The virus writer creates an RSA key:
• The public key appears in the body of the virus.
• The private key is kept by the author.
• The virus spreads and the payload uses the public key. For example, it ciphers the data (hard drives, files, e-mail, whatever) of the targets with the public key.
• The virus writer requires a ransom before sending the private key.

Even if you’re not into Cryptology, I strongly recommended this reading.

Part 1 & Part 2

Source: Security Focus