A man has been arrested in connection with the theft of source code from Cisco in May, Scotland Yard has confirmed.

The Met's Computer Crime Unit searched residences in Manchester and Derbyshire in early September, confiscated computer equipment and arrested a 20 year-old man suspected of committing hacking offences under the Computer Misuse Act of 1990.

The police would not discuss the specifics of the case, but did say the arrest was linked to the Cisco source code theft. The suspect has since been released on bail and been ordered to appear at the police station again in November. Computer equipment seized in the searches is being forensically examined.

A Cisco spokesman said the company is encouraged that an arrest was made in the case. "As we have previously reported, we are continuing to co-operate with law enforcement agencies on this matter," read a statment. "We view the arrest as what will likely be one of many steps in this matter. We will take every measure to protect our intellectual property."

The arrest marks a major breakthrough in the case, which involves the posting of more than 800MB of source code from Cisco's Internetwork Operating System (IOS) to a Russian website in May. IOS is a proprietary operating system that runs on much of the networking hardware that Cisco makes.

Malicious hackers made off with code for versions 12.3 of IOS after the thief compromised a Sun server on Cisco's network, then briefly posted a link to the source code files on a file server belonging to the University of Utrecht in the Netherlands, according to Alexander Antipov, a security expert at Positive Technologies, a security consulting company in Moscow.

Antipov said he downloaded more than 15MB of the stolen code after an individual using the online name "Franz" briefly posted a link to a 3MB compressed version of the files in a private Internet Relay Chat forum on in May.

The link provided was only available for approximately ten minutes and pointed to a file on an FTP server which belongs to the University of Utrecht in the Netherlands. That server is open to the public for hosting files of files smaller than 5MB, according to the University's Web page.

Antipov subsequently posted some of that code on a Russian security Web site, www.securitylab.ru, to call attention to the reported theft, but denied knowing Franz. At the time, Cisco said it was working with the FBI to pursue the hackers.

The arrest in the Cisco theft follows other recent successes in cybercrime cases. In June, the FBI announced arrests in the source code theft for a much-anticipated version of the popular computer game Half-Life from the network of game maker Valve.

In May, German police arrested men in connection with creating the Sasser Internet worm and a Trojan horse program called Agobot. On 9 September, prosecutors in Verden, Germany, indicted an 18-year-old student in the Sasser worm case.