Federal employees at the Office of Personnel Management are also suing the government, claiming that Musk had a private server installed that has not been vetted or approved for security. OPM's systems contain sensitive employee records for tens of millions of current and former federal workers, and the hack and theft of OPM records by Chinese hackers in 2015 is considered among the worst federal security breaches of all time. The use of a private email server by then-Secretary of State Hillary Clinton was the subject of a criminal investigation by the FBI during the 2016 election and was bitterly criticized by Trump and Republicans at the time as a massive security lapse.