Hackers compromised a Federal Bureau of Investigation email system on Saturday and sent tens of thousands of messages warning of a possible cyberattack, according to the agency and security specialists.
Fake emails appeared to come from a legitimate FBI email address ending in @ic.fbi.gov, the FBI said in a statement.
Although the hardware impacted by the incident "was taken offline quickly upon discovery of the issue," the FBI said, "This is an ongoing situation."