Email accounts used by the Treasury Department's senior leadership were compromised by suspected Russian government hackers who carried outagainst several U.S. federal agencies, according to Senator Ron Wyden of Oregon. The ranking Democrat on the Senate Finance Committee said the "full depth" of the Treasury hack "isn't known."
Senate Finance Committee staff were briefed about a major breach of the Treasury as part of the, Wyden said in a statement Monday night.
"Hackers broke into systems in the Departmental Offices division of Treasury, home to the department's highest-ranking officials. Treasury still does not know all of the actions taken by hackers, or precisely what information was stolen," Wyden said.
The Internal Revenue Service said there was no evidence the agency was compromised or taxpayer data affected, Wyden added.
Wyden said Microsoft alerted the department to the compromise, which began in July.
Cybersecurity experts believe a sophisticated group of hackers was able to enter U.S. government networks earlier this year via a loophole in products developed by SolarWinds, which provides software for government agencies and large companies.
The hackers were then able to access sensitive information and communications of SolarWinds clients, including the departments of Treasury, Commerce and Energy and Los Alamos National Laboratory, which oversees the country's nuclear weapons.
President Trump has the cyber-espionage campaign, suggesting China could be the culprit, but top U.S. officials, including Secretary of State Mike Pompeo and Attorney General William Barr, have pointed fingers at Russia.
"This was a very significant effort, and I think it's the case that now we can say pretty clearly that it was the Russians that engaged in this activity," PompeoFriday in an interview on the conservative radio program "The Mark Levin Show."
, saying during a press conference on Monday that it "certainly appears to be the Russians."
The Kremlin has denied responsibility.