By Jim Finkle BOSTON (Reuters) – Cybersecurity company FireEye Inc has acquired Mandiant Corp, the computer forensics specialist best known for unveiling a secretive Chinese military unit believed to be behind a series of hacking attacks on U.S. companies. FirEye shares jumped more than 20 percent after Thursdays announcement of the $1.05 billion cash-and-stock deal, which FireEye said closed on Monday. It unites two companies with relatively new technologies for thwarting cyber attacks, and brings together two of the most-respected executives in the security industry: FireEye CEO Dave DeWalt and Mandiant founder Kevin Mandia. While sales of older anti-virus products have been on the decline, security experts expect strong growth in both FireEyes cloud-based systems for detecting malicious software and Mandiants software that analyzes cyber attacks.