A global investigation into the theft of a key piece of software that forms the "backbone" of the worldwide web has led to an arrest of a suspected teenaged hacker in Sweden.

The news followed claims that an internet break-in at Cisco Systems in California last year, which led to a hacker accessing part of Cisco's IOS source code, was just one part of an extensive operation in which thousands of systems were penetrated.

It is believed that the case has involved attacks on computer systems involving the United States military, NASA and university research laboratories. The CIA and and Scotland Yard were among the organisations that investigated the Cisco attack.

Shortly after its theft, the Cisco code was posted on a Russian website in an move designed to prove it had been stolen, to the obvious embarrassment of Cisco, whose products include secure business networks.

The implications of the event caused a storm within the IT industry. Experts said that access to the source code could provide sophisticated hackers with the means of compromise the security of computers running the affected software.

The stolen software is used to power routers which control the flow of information over the internet. This includes Cisco's 7000 series, which forms the worldwide web's spine.

The software giant said it was "encouraged" by news of the detention in Sweden, which had involved "the help of many law enforcement agencies".

"Cisco IOS source code is both copyrighted and protected as proprietary material," it added.

"It is illegal to post it, make it available to others, download it or use it. Cisco will take all appropriate legal actions to protect its intellectual property."

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