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By | John Leyden 9th July 2008 17:47

Shocker DNS spoofing vuln discovered three years ago by a student

The mad woman in the attic

A flaw in how the internet's addressing system works that sparked a patching frenzy on Tuesday night may has first been uncovered by a student as long as three years ago.

Shortcomings in how the Domain Name System protocol is implemented by multiple vendors facilitate DNS cache poisoning attacks, security clearing house US CERT warned on Tuesday. Successful exploitation of these security shortcomings creates a means for hackers to spoof DNS replies, allowing for the redirection of network traffic or to mount man-in-the-middle attacks.

Security researcher Dan Kaminsky deserves a lot of credit for realising the seriousness of the flaw and working behind the scenes with multiple vendors over recent months leading up to co-ordinate this week's patching activities. But Kaminsky may not have been the first to discover the flaw, only the first with enough clout to mobilise action.

Three years ago Ian Green, then studying for his GIAC Security Essentials Certification (GSEC), submitted a paper that details the same DNS spoofing vulnerability, the SANS Institute's Internet Storm Centre notes.

In order to spoof a DNS request it's necessary to "guess" both the Query ID and the source port. The query ID is 16 bits long, and the UDP source port also has over 60,000 potential option. But as Green noted back in January 2005, DNS transactions are incremented by one for each subsequent query while the UDP source port remains the same during a session.

Although the weaknesses of the DNS protocol have been known for some time, Kaminsky's upcoming presentation at Black Hat next month is sure to put what has been a peripheral, forgotten issue (something like the mad woman in the attic) into the full view of the public. Details of new tools designed to exploit the vulnerability or exploits already in the wild are likely to emerge. ®

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