Hackers working for a nation-state recently invaded the safety system of a critical infrastructure facility in what cyber experts call “a watershed attack” that halted plant operations. Cybersecurity firm FireEye disclosed the incident on Thursday, saying it targeted Triconex industrial safety technology from Schneider Electric SE. Schneider confirmed that the incident had occurred and that it had issued a security alert to users of Triconex, which cyber experts said is widely used in the energy industry, including at nuclear facilities, and oil and gas plants. FireEye and Schneider declined to identify the victim, industry or location of the attack.