A Japanese naval officer unwittingly leaked top-secret data on an advanced US military system when swapping porn files at work, a newspaper said today.

The Yomiuri Shimbun said the data was leaked when the petty officer second class had copied pornographic images -- accompanied by the sensitive files -- from a colleague's computer and circulated them to a third officer.

The data found on the officer's computer included formulas for the Aegis interceptor system and data on its radar's capacity to track several targets at once, the Yomiuri said.