US federal investigators are applying pressure on senior government officials suspected of leaking details about the US government's role in developing the Stuxnet malware, according to a report by the Washington Post.
The FBI and US prosecutors are analysing email accounts and phone records as well as interviewing current and former officials in a search to find links to journalists, according to the report on Saturday.
The investigation is likely to centre on a small circle of senior officials, given the highly classified nature of the cyberattacks against Iran, details of which were published in a report by The New York Times in June 2012.
The report said Stuxnet was the product of a joint effort between the US government and Israel's military, codenamed 'Olympic Games'. The programme began in the Bush Administration in 2006 and was accelerated under Obama's command.
Stuxnet was designed to target a specific configuration of Siemens programmable logic controllers in use at Iran's Natanz uranium enrichment plant, the NYT said.
A round of Department of Justice investigations into "possible unauthorised" leaks that appeared in newspapers and books began shortly after the NYT report, however at the time, the department did not say which of several highly classified leaks were the subject of the investigations since that could implicitly confirm the stories.
Shortly after Olympic Games became public, Obama highlighted his office's "zero tolerance" attitude towards leaks. The Obama administration has prosecuted six people accused of leaking confidential information.