When a company holds the personal information of 1 billion people, it can't take security lightly. Ars Technica details the stress tests that Facebook puts its security team though, testing their employees' abilities to respond to an attack. The tests were conceived by Facebook executives, and responders were kept in the dark about each operation. In one instance, the team discovered a mysterious laptop plugged into their network, and on another occasion, an FBI agent tipped them off to a breach from an IP in Beijing. The team was able to address the latter issue in a matter of hours, but to Facebook's executives, the most important lesson was in how well their team could work together and how quickly they could mobilize against a serious breach.