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.
In April 2008, Damballa released instructions for removing Kraken malware from computers and a list of IPs comprising the Kraken botnet. The list shows that on April 13, 2008, there were 495,000 computers in the Kraken botnet.