F5 Networks has acquired a DDoS prevention startup called Defense.net

F5 Networks has acquired Defense.net, an 18-month-old startup that helps customers prevent distributed denial-of-service attacks to servers with a cloud-based security product. The deal will help Seattle-based F5 compliment its software offering, which already includes an existing on-premise DDoS Protection service. Belmont, California-based Defense.net was founded in December 2012 and had previously raised $9.5 million.

Network hardware and software vendor F5 has bought Defense.net, a security startup with cloud-based service for blocking distributed denial of service (DDoS) attacks that hit lots of servers and can bring down websites. As a result of the deal, F5 will bolster its software lineup, which includes software for staving off DDoS attacks that hit companies’ on-premises data centers. Barrett Lyon, who also founded DDoS mitigation company Prolexic, started Defense.net in late 2012. (Content-distribution network company Akamai bought Prolexic last year.) Lyon also was a character in the cyber thriller “Fatal System Error” by Joseph Menn.