Cisco Systems is investigating a potential security breach after Russian web site SecurityLab.ru reported that it had received some of Cisco's source code from hackers. Some of the code has also been leaked onto the internet, according to the Russian security firm.

"Cisco is aware that a potential compromise of its proprietary information occurred and was reported on a public web site just prior to the weekend," Jim Brady, spokesman for the internet networking company, told CNET News.com. "The Cisco information security team is looking into this matter and investigating what happened."

According to reports, as much as 800MB of code may have been stolen, although Cisco has made no comment on this, other than to tell internetnews.com that "Based on preliminary data, we don't believe any confidential customer information or financial systems were affected".

The implications of the leak, if found to be genuine, are unclear. Some speculate that the code could help hackers exploit potential vulnerabilities in the Cisco systems; others disagree, saying they don't need to code to do this. At the very least the security breach will be embarrassing for Cisco, which is trying to gain ground in the security sector.

In February, portions of Windows 2000 and Windows NT 4.0 were posted onto the internet, forcing Microsoft to write to those who downloaded the code, warning that it is illegal to post the code, make it available to others, download it or use it.

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