The US Treasury Department has slapped sanctions on nine Iranians, including members of an NGO accused of spying and members of an Iranian military unit.
While working with a dual Iranian-US citizen, who was only identified in court papers as Individual A, Witt divulged "the existence of a highly classified intelligence collection program" and risked the life of an intelligence colleague by revealing his true identity, said John Demers, the assistant attorney general for national security.
Iranian hackers then set up fake Facebook personas to befriend those agents and attempt to install spyware that would track their computer activity, the indictment said.
Officials would not elaborate on why the indictment was brought six years after her detection, except to say that they had to move classified intelligence into an unclassified format to be used in a pending criminal proceeding.
Authorities said Ms. Witt's activities caused "serious damage" to US intelligence activities. According to authorities, she started working on behalf of Tehran by disclosing classified information and compiling research on US intelligence personnel she previously worked with. "Thanks for giving me the opportunity".
Four other Iranians also were named in the indictment and face charges of conspiracy, computer intrusions and identity theft in connection with targeting Witt's former co-workers in 2014 and 2015.
Media captionIranians braved the snow in Tehran to mark their country's 1979 Islamic Revolution.
That year she travelled to Iran to attend an anti-America conference sponsored by the Revolutionary Guard-related New Horizon Organization. The conference's main topic was condemning American moral standards, promoting anti-US propaganda, anti-Semitism, and Holocaust denial.
During her time in the military, she had top secret clearance, the indictment says, which gave her access to intelligence materials that contained the real names of American sources and clandestine agents.
The Department of Treasury accuses Net Peygard Samavat Company of being "involved in a malicious cyber campaign to gain access to and implant malware on the computer systems of current and former counterintelligence agents".
A 2012 photo released by the Department of Justice shows Monica Elfriede Witt.
A previously issued Federal Bureau of Investigation missing persons poster said she was working as an English teacher in either Afghanistan or Tajikistan, and had lived overseas for more than a year before vanishing.
In the indictment, Witt, who converted to Islam, is also identified by her Iranian names, Fatemah Zahra and Narges Witt.
The charging documents outline a series of electronic messages between Witt and Individual A, who resided primarily in Iran, before she defected.
The Justice Department has issued arrest warrants for Witt and the four Iranians, who all remain at large.
Iran and the United States are longtime cyber-antagonists.
Diplomats are expected to discuss Iran during a US-led two day summit on "peace and security" that began on Wednesday in Warsaw.
"She chose not to heed our warning that travel to Iran could potentially make her susceptible to recruitment", Tabb said.