Wednesday, July 22, 2009

The economics of Botnets

In the past ten years, botnets have evolved from small networks of a dozen PCs controlled from a single C&C (command and control center) into sophisticated distributed systems comprising millions of computers with decentralized control. Why are these enormous zombie networks created? The answer can be given in a single word: money.

A botnet, or zombie network, is a network of computers infected with a malicious program that allows cybercriminals to control the infected machines remotely without the users’ knowledge. Zombie networks have become a source of income for entire groups of cybercriminals. The invariably low cost of maintaining a botnet and the ever diminishing degree of knowledge required to manage one are conducive to growth in popularity and, consequently, the number of botnets.

So how does one start? What does a cybercriminal in need of a botnet do? There are many possibilities, depending on the criminal’s skills. Unfortunately, those who decide to set up a botnet from scratch will have no difficulty finding instructions on the Internet.

You can simply create a new zombie network. This involves infecting computers with a special program called a bot. Bots are malicious programs that unite compromised computers into botnets. If someone who wants to start a ‘business’ has no programming skills, there are plenty of ‘bot for sale’ offers on forums. Obfuscation and encryption of these programs’ code can also be ordered in the same way in order to protect them from detection by antivirus tools. Another option is to steal an existing botnet.

The cybercriminal’s next step is to infect user machines with bot malware. This is done by sending spam, posting messages on user forums and social networks, or via drive-by downloads. Alternatively, the bot itself can include self-replication functionality, like viruses and worms.


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