Any helicopter in the fleet carrying the president is known as Marine One
The US military is investigating how technical data about a helicopter used in President Barack Obama's fleet was found on an Iranian computer.
Reports say the data had been on a computer belonging to an executive of a defence contractor which was also being used to share files over the internet.
Analysts say hackers are increasingly using music and video file sharing networks to access sensitive data.
The Pentagon said the risk of someone exploiting the data was very low.
The discovery was made by data monitoring firm Tiversa, which monitors peer-to-peer file sharing networks for government agencies and large enterprises.
Keith Tagliaferri, director of operations at Tiversa, said the employee who inadvertently disclosed the information was a high-level executive - and the breach had taken place outside the company's offices.
The file was found on an Iranian computer on 25 February.
Tiversa did not name the contractor, or give any information about the Iranian computer.
The company said it had also alerted federal officials and a defence contractor about the "open window" last October.
Pentagon spokesman Geoff Morrell said the information accessed about the aircraft - a Sikorsky VH-60 - is unclassified.
He said the VH-60 is used to carry White House staff and guests. A larger Sikorsky helicopter, the V-3, is used for the president.
Navy spokesman Lt Clayton Doss said the service was "looking into the matter".
He said that even though the helicopter data was "relatively dated", the information "should not have been made available on the internet or placed in the public domain".
He added that Sikorsky was not the source of the breach.
The White House's current fleet of 19 helicopters was built by Sikorsky Aircraft more than 30 years ago.
Lockheed Martin currently has a multibillion-dollar contract to replace the fleet.
Company spokesman Troy Scully said it had been told by Tiversa that it was not the source of the breach.