Hackers compromise FBI email system

Hackers broke into the Federal Bureau of Investigation's email system on Saturday, sending tens of thousands of messages warning of a possible cyberattack, according to the agency and security specialists.

The FBI said that messages appeared to come from a legitimate company email address.

It added that hardware impacted by the incident was taken quickly offline.

A copy of an email posted on Twitter showed a subject line of "Urgent: Threat actor in systems."

It also appeared to end with a sign-off from the Department of Homeland Security.

The FBI is part of the Department of Justice.

Bloomberg News first reported the incident on Saturday.