Dan Farmer (born April 5, 1962) is an American computer security researcher. In a summer course in 1989, in order to graduate from Purdue University he started the development of the COPS program for identifying security issues on Unix systems under Gene Spafford, first releasing it after leaving Purdue in late 1989. In 1995, he and Wietse Venema created Security Administrator Tool for Analyzing Networks (SATAN), one of the earliest network based vulnerability scanners.
SATAN was a controversial program when it was released, because some security administrators and law enforcement personnel believed that hackers would use it to identify and break into private networks. The release of SATAN led SGI to fire Dan Farmer. With Venema, Farmer authored Forensic Discovery, a book about forensic techniques for gathering digital evidence. Dan Farmer was the CTO of Elemental Security, a company he co-founded with Dayne Myers.