The U.S. Cybersecurity and Infrastructure Security Agency (CISA) issued an alert on Thursday, not naming the agency but providing technical details of the attack. Hackers, it said, gained initial access by using employees legitimate Microsoft Office 365 log-in credentials to sign onto an agency computer remotely. CISA s investigation turned up no definitive answer however, it speculated that it could have been a result of a vulnerability exploit that it said has been rampant across government networks.
Source: https://threatpost.com/feds-cyberattack-data-stolen/159541/