In the spy vs. spy scenarios sparked by NSA-gate and increasing evidence that everyone — not just the NSA — is spying on everyone else, it makes perfect sense that FireEye (s feye) is buying Mandiant for a cool $1 billion. Mandiant a specialist in cyber threat forensics and endpoint detection, came to prominence last year for its starring role in a New York Times report that linked a Shanghai-based unit of the Chinese People’s Liberation army to cyber attacks on U.S.-based tech companies.

According to a press release, the deal brings together the two companies’ respective expertise in “real-time threat detection, contextual threat intelligence and rapid incident response.”

FireEye, an expert in persistent threat detection, and Mandiant had already been working together for a year, and now they’re formalizing that collaboration to offer a range of cybersecurity detection, prevention, containment and remediation. Mandiant also brings its expertise in end-point security…