The hacker, known as "Guccifer," gained access to Blumenthal's AOL email account last week and sorted out all memos the senior White House adviser to President Bill Clinton sent to the former secretary of state, TheSmokingGun reported Monday.
In a series of weekend email blasts, Guccifer sent four of the emails discussing the Sept. 11 attack on the U.S. consulate in Benghazi, Libya, to congressional aides, political figures and journalists.
Guccifer's location remains a mystery to authorities because hackers are known for their ability to conceal their trail through proxies, Internet protocol spoofing and anonymizing software, TheSmokingGun said.
Two IP addresses connected to Guccifer's recent online maneuvers trace him to Russia. The hacker did show another connection to Russia by forwarding Blumenthal's emails to Russian journalists even though most of the other journalists he sent them to were based in the United States.