Ranum helped design and implement Digital Equipment Corporation's Secure External Access Link , regarded as the first commercial bastion host firewall, in 1990. He left DEC to work for Trusted Information Systems as chief scientist and development manager for Internet security products. It was at TIS that Ranum became responsible for the whitehouse.gov Internet email site. Once charged with that responsibility, Ranum advocated that the whitehouse.com domain be registered as well. Despite his advice, it was not registered by the government, but was later registered for an adult entertainment provider. At TIS, he developed the TIS Internet Firewall Toolkit under a grant from DARPA. After TIS, he worked for V-One as chief scientist, and was extensively involved in that company's IPO. Three months after that IPO, Ranum formed his own company, Network Flight Recorder, and served as CEO for three years before stepping into a CTO role. Ranum later left NFR to consult for TruSecure, before joining Tenable Network Security as CSO. In addition to his various full-time positions, Ranum has also held board or advisory positions at NFR Security, Protego Networks, and Fortify Software.
Public presentations
Ranum has spoken to USENIX audiences at LISA 1997, 1999 LISA 2000, 2002, and 2003. He spoke out against full disclosure at the Black Hat Security Briefings in 2000. More recently, Ranum has spoken at Interop in 2005 and 2007, CanSecWest in 2010, and Secure360 in 2011. He previously taught courses for the SANS Institute.
Influence
Ranum's work has been cited in at least 15 published U.S. patents, as well as numerous other computer and network security articles and books.
Marcus has co-authored a series of "Face Off" articles with Bruce Schneier, which have appeared approximately bi-monthly in Information Security Magazine since July, 2006. Ranum is one of a number of editors of the SANS Newsbites semiweekly email newsletter.
Currently, Ranum lives in Morrisdale, Pennsylvania. His hobbies include photography and firearms. He maintains an active stock photography account on DeviantArt, and he wrote an essay for Oleg Volk's pro-firearms site. . Marcus Ranum was also interviewed by digital artist for the NWFLAA which can be read in 2 parts: and . He is an atheist, maintaining a blog on the Freethought Blogs network.