The United States government on Tuesday said that Russia was “likely” behind a massive hack of government and private company networks discovered last month.
The government said that it was still trying to understand the scope and mitigate a “significant cyberincident” involving both government and nongovernmental networks.
“At this time, we believe this was, and continues to be, an intelligence-gathering effort,” the statement said, and added: “This is a serious compromise that will require a sustained and dedicated effort to remediate”.
Departments penetrated in the hack include Defense, State, Homeland Security, Treasury, and Commerce and is considered the worst known cyber-compromise in recent history.
The security company FireEye, which was itself breached, discovered the new round of attacks. Other attacks have used resellers of Microsoft cloud services, with email being a main target of the hackers.
Russia has denied involvement in the hack.