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By | Dan Goodin 24th July 2008 18:10

Exploit code for Kaminsky DNS bug goes wild

Still think threat is exaggerated?

When Dan Kaminsky disclosed a critical flaw in the net's address lookup system earlier this month, he said it was crucial internet service providers and other organizations install patches immediately. He wasn't kidding.

Security researchers have developed two working exploits that poison vulnerable domain name system servers, allowing attackers to redirect unwitting end users to impostor sites. What's more, the attack code has been added to Metasploit, a penetration testing tool used to test the security of computers and networks. The program, which is maintained by HD Moore, makes it easy for white hats and black hats alike to exploit vulnerable servers.

Some people have complained that Kaminsky's bug has been shamelessly hyped. We disagree. Should there be widespread exploitation of the flaw, the result would be chaos. Attackers could taint the machines relied on by millions of people. When they typed into their browser, they'd have no way of knowing whether they were being directed to the real site or one designed to steal their money. Trust on the internet, as flawed as it may be now, would completely break down.

Much of the attack code was written by |)ruid, a researcher from the Computer Academic Underground. According to Moore, it could be used like this:

1. Bad Guy probes the target DNS to see if it's vulnerable (a couple free services can do this)

2. Bad Guy picks a domain they want to hijack for users of that DNS Server

3. Bad Guy runs the bailiwicked_domain module and takes control of that domain in the cache of that server

At this point, anyone who uses that vulnerable DNS server is going to see the wrong DNS server record for the poisoned domain

The exploits are available here and here.

Currently, the exploits work only on caching servers used by ISPs and other large organizations, but Moore said they could be modified to work against client-side resolvers, which are used on desktop machines. Earlier this month, Microsoft issued an update patching the vulnerability. It was unclear if other OSes are vulnerable.

Moore said plenty of ISPs have yet to install the patch. To test whether your service is vulnerable, go here and click the button that says "check my DNS." If you find a service that's vulnerable, please leave a comment, or email me here (and be sure to include the IP address of the offending server). ®

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