“The attacker primarily sought information related to certain government customers,” he wrote.
The blog did not say who might have carried out the attack. The firm and the FBI are investigating the hack.
FireEye share price plunged following the company’s acknowledgment of the hack.
What did FireEye say?
“We are witnessing an attack by a nation with top-tier offensive capabilities,” Mr Mandia said in Saturday’s blog, adding that it was “different from the tens of thousands of incidents we have responded to throughout the years”.
“The attackers tailored their world-class capabilities specifically to target and attack FireEye,” he warned adding that they used “methods that counter security tools and forensic examination”.
“They used a novel combination of techniques not witnessed by us or our partners in the past,” the blog said.
California-based FireEye was set up in 2004. It specializes in investigating attacks in cyberspace against companies throughout the world.
It is being described as one of the fastest-growing firms in the industry.