Okena

Okena is an intrusion detection company based in Waltham, Massachusetts. It was acquired by Cisco Systems on January 24, 2003, for $154M, in an all-stock transaction.
Okena's technology is behavior-based detection and prevention, as opposed to most Intrusion Detection Systems, which are binary-pattern-based. Also, the Okena endpoint agent can block certain behaviors and attacks, an early example of Intrusion Detection and Prevention Systems. Okena's StormWatch endpoint security software formed the basis of the Cisco [Security Agent].
Okena was founded in 1999 by Todd Brennan and Allen Hillery. It was initially located in Cambridge, MA.