Cisco is investigating claims that parts of its IOS network infrastructure software source code have been posted on the internet.
Russian security website SecurityLab claims a hacker has been boasting of this exploit online, and has seen two samples of the source code for versions 12.3 and 12.3T of the software.
The hacker displayed 2.5MB of code, according to SecurityLab, and hinted that he may have as much as 800MB.
Cisco said in a statement: "Cisco is aware that a potential compromise of its proprietary information occurred and was reported on a public website just prior to the weekend.
"The Cisco information security team is looking into this matter and investigating what happened."
The company said that its IOS software is the most widely used network infrastructure software in the world.
This is the second time this year that source code belonging to a major company has been posted on the internet. In February, code for Internet Explorer 5 was posted online without Microsoft's consent.
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