Security startup Defense.net recently came out of stealth mode and announced $9.5 million in funding led by Bessemer Venture Partners. Bessemer partner David Cowan has joined the Defense.net board.

The company, which was founded in December of 2012 by Prolexic Technologies founder Barrett Lyon, is focused on mitigating modern distributed denial of service (DDoS) attacks as they grow in scale and sophistication.

Other Defense.net employees include Prolexic veterans Joe Daly as vice president of network operations and Dan Murphy as director of systems architecture.

"A decade ago, small scale DDoS attacks by today's standards shut down offshore cyber casinos for extortion purposes, but now political hacktivists and foreign government backed 'cyber fighters' such as Izz ad-Din al-Qassam are attacking critical infrastructure of the U.S., including financial institutions, utilities, telcos, Internet hosting facilities, and state government," Lyon said in a statement. "Although much of this critical infrastructure uses traditional DDoS mitigation solutions, every week brings reports of sites, applications, and services brought down by attacks that are now significantly more sophisticated and 16 times larger than just one year ago; clearly the techniques we developed in 2003 don't work for global banks today."

"Banks, utilities, governments and other organizations face increasing threats from more formidable antagonists wielding a growing arsenal of DDoS weapons," Bessemer's Cowan said in a statement. "Existing defenses are falling down on the job and taking down many of their customers when it happens; so we backed Lyon and his all-star DDOS team because they have the vision and unparalleled experience to deliver seamless and scalable business continuity."