Cisco Systems, Inc. (NASDAQ:CSCO) announced today that it will buy rival Sourcefire, Inc. (NASDAQ:FIRE) at $76 per share, approximately $2.7 billion. The deal has been approved by each companies’ board of directors and is expected to be completed before the end of the year. “Sourcefire aligns well with Cisco’s future vision for security and supports the key pillars of our security strategy. Through our shared view of the critical role the network must play in cyber security and threat defense, we have a unique opportunity to deliver the most comprehensive approach to security in the market,” said Cisco vice president Hilton…