Retired Marine Gen. James "Hoss" Cartwright has been told he is a target of the probe, NBC News and The Washington Post reported Thursday. A "target" is someone a prosecutor or grand jury has substantial evidence linking to a crime and who is likely to be charged.
The Justice Department referred questions to the U.S. attorney's office in Baltimore, where a spokeswoman, Marcia Murphy, declined to comment.
The investigation of the leak about the Iran cyberattack is one of a number of national security leak investigations that have been started by the Obama administration, including ones involving The Associated Press and Fox News.
In June 2012, the New York Times reported that Cartwright was a crucial player in the cyber operation called Olympic Games, started under President George W. Bush.
Bush reportedly advised President Barack Obama to preserve Olympic Games.
According to the Times, Obama ordered the cyberattacks sped up, and in 2010 an attack using a computer virus called Stuxnet temporarily disabled 1,000 centrifuges that the Iranians were using to enrich uranium.
Congressional leaders demanded a criminal probe into who leaked the information, and Obama said he had zero tolerance for such leaks. Republicans said senior administration officials had leaked the details to bolster the president's national security credentials during the 2012 campaign.
The Times said Cartwright was one of the crucial players who had to break the news to Obama and Vice President Joe Biden that Stuxnet at one point had escaped onto the Internet.
An element of the program accidentally became public in the summer of 2010 because of a programming error that allowed it to escape Iran's Natanz plant and sent it out on the Internet, the Times reported. After the worm escaped onto the Internet, top administration officials met to consider whether the program had been fatally compromised.
Obama asked if the program should continue, and after hearing the advice of top advisers, decided to proceed.
Cartwright, a four-star general, was cleared in February 2011 of misconduct involving a young aide. An anonymous accuser had claimed Cartwright acted inappropriately during a 2009 overseas trip on which the aide traveled as a military assistant. Several sources confirmed that the former aide was a young woman.
The Pentagon inspector general quickly cleared Cartwright of the most serious allegations, which involved claims that he may have had an improper physical relationship with the woman. The report did find that Cartwright mishandled an incident in which the aide, drunk and visibly upset, visited his Tbilisi, Georgia, hotel room alone and either passed out or fell asleep on a bench at the foot of his bed. Cartwright denied any impropriety and was later cleared of all wrongdoing.
Cartwright, once considered the leading candidate to become Joint Chiefs of Staff chairman, resigned from the military in August 2011.
NBC said Cartwright did not respond to request for comment and that his attorney, former Obama White House counsel Greg Craig, said he had no comment.