New employees and contractors will be left in clearance limbo as OPM cleans up its system.

The shutdown happened after OPM conducted an internal review that showed a vulnerability in its background check system, E-QIP, though the office explained that it hadn't found evidence that hackers had actually exploited the flaw.

The actions OPM has taken are not the direct result of malicious activity on this network, and there is no evidence that the vulnerability in question has been exploited. Rather, OPM is taking this step proactively, as a result of its comprehensive security assessment, to ensure the ongoing security of its network.