BotHunter is a passive network monitoring tool designed to recognize the
communication patterns of malware-infected computers within your network
perimeter. Using an advanced infection-dialog-based event correlation engine
(patent pending), BotHunter represents the most in-depth network-based
malware infection diagnosis system available today. Most people whose
computers have been turned into bots and linked to a botnet have no idea that
their machines have been commandeered by cybercriminals. (in Internet)