STOCKHOLM (Reuters) - An unidentified computer hacker has got hold of top secret U.S. computer system codes for guiding space ships, rockets and satellites, a lawyer in Sweden said Friday.

Computer experts raided the offices of an information technology company in Stockholm last month and found a copy of the source codes for the software program OS/COMET developed by U.S. firm Exigent Software Technology, Johan Starell, legal counsel for Exigent in Sweden, told Reuters.

A source code contains full details of how a software program works.

OS/COMET has been deployed by the U.S. Air Force on the NAVSTAR Global Positioning System (GPS) Colorado Springs Monitor Station, Exigent said in a statement in December.

The suspected source codes theft, carried out remotely over the Internet on Christmas Eve last year from the U.S. Naval Research Laboratory in Washington D.C., was detected on December 27.

The U.S. Federal Bureau of Investigation (FBI (news - web sites)) was put on the case. The trail led to Freebox.com, an Internet Web server run by the Swedish IT company Carbonide, Starell said.

``A stolen source code was found on their server but nothing indicates they had anything to do with getting it there,'' Starell told Reuters.

Analyses of the Carbonide server accessed by the hacker known only by the username ``LEEIF'' showed that the perpetrator had been able to hide his or her true identity by breaking into the account of a genuine Freebox.com client and using that person's Internet account.

``We couldn't get any further information about where it came from or find out if it had been copied and sent elsewhere,'' he said.

``Sweden seems like a closed chapter. We can't get any further here,'' he added.