The Texas native served in the Air Force between 1997 and 2008, where she was trained in Farsi - the predominant language of Iran - and was deployed overseas on classified counterintelligence missions, including to the Middle East.
The Justice Department said Tuesday that Witt, who remains at large, held high-level security clearances before she defected to Iran in 2013.
The indictment also alleges that Witt planned to go to Russian Federation in 2013 to contact WikiLeaks without disclosing her location.
Billing itself as an "anti-imperialist, anti-Zionist" think tank, New Horizon organized conferences in Iran that cast a critical eye on USA and Israeli policy worldwide and stoked accusations of anti-Semitism from Western critics. Officials believe she still lives in Iran.
After Witt returned to the U.S., Federal Bureau of Investigation agents conducted a defensive briefing with her to warn her that she might be the target of recruitment by Iranian security services.
A Farsi language specialist, she was deployed to the Gulf area several times on signals intelligence missions, according to the indictment, and had top security clearance giving her access to the identities of clandestine USA agents and informants in the field.
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A U.S. Air Force veteran and former counterintelligence agent was charged Wednesday with spying on behalf of the Iranian government.
After leaving the armed forces in 2008, Witt worked as a contractor for two years, officials said. The connections she made at that event with dual Iranian-American citizens enabled her to defect the following year. The Justice Department said the information threatened other agents in the US intelligence community, a federation of 16 agencies.
She attended the same conference the following year and was hired by an unnamed individual to assist in the filming of an anti-American propaganda commercial.
She wrote Individual A that she wanted to put her Air Force training "to good use instead of evil". That's a reference to Edward Snowden, a former NSA contractor who leaked classified US information.
Witt maintained contact with an IRGC member she met at the conference and eventually defected to the Islamic Republic.
Iranian hackers are accused of setting up fake social media accounts to befriend the agents that Witt provided information on to try and install spyware to their computers.
She also conducted online research, including on Facebook, to create information "packages" on her former colleagues in the USA intelligence community.
Jay Tabb, the FBI's executive assistant director for national security, said investigators believe Witt shared information that "could cause serious damage to national security", though he declined to provide specific details of the operations she allegedly disclosed.