KRAKENKraken

The Kraken botnet was the world's largest botnet as of April 2008. Researchers say that Kraken infected machines in at least 50 of the Fortune 500 companies and grew to over 400,000 bots. It was estimated to send 9 billion spam messages per day. Kraken botnet malware may have been designed to evade anti-virus software, and employed techniques to stymie conventional anti-virus software.