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7/23/2008
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Red Alert! DNS Flaw Revealed

Security researchers warn users to patch immediately, as technical details to exploit a widespread DNS vulnerability were disclosed online.

"Patch. Today. Now. Yes, stay late."

That's the word from security researcher Dan Kaminsky, who recently presided over an unprecedented effort to coordinate a fix for a DNS vulnerability across more than 80 software and hardware vendors.

And now the danger flare has been fired to warn computer users everywhere that the risk is real. Technical details about how one might exploit the vulnerability have been disclosed.

The domain name system translates domain names, like "informationweek.com," into numeric IP addresses and vice versa. The DNS flaw, if exploited, allows what is known as DNS cache poisoning. This involves remapping domain names to different, potentially malicious servers.

US-CERT on Monday warned: "Technical details regarding this vulnerability have been posted to public Web sites. Attackers could use these details to construct exploit code. Users are encouraged to patch vulnerable systems immediately."

"This is a very serious situation, and can possibly lead to widespread and targeted attacks which hijack sensitive information by redirecting legitimate traffic to fraudulent Web sites, due to incorrect (fraudulent) information being injected into the vulnerable caching nameserver(s)," Trend Micro security researcher Paul Ferguson said in a blog post.

Kaminsky has been planning to present details about the DNS vulnerability at the Black Hat security conference in two weeks.

Security researchers just couldn't wait, however, and have been speculating about the nature of Kaminsky's findings.

On Monday, one such researcher, Halvar Flake, posted his guess about how the DNS vulnerability worked on his blog.

A researcher at Matasano Security then corrected some of the details in a blog post of his own, and the cat was out of the bag.

The post on the Matasano blog was promptly unpublished and replaced with an apology from Thomas Ptacek, a principal at the company.

"Earlier today, a security researcher posted their hypothesis regarding Dan Kaminsky's DNS finding," said Ptacek. "Shortly afterwards, when the story began getting traction, a post appeared on our blog about that hypothesis. It was posted in error. We regret that it ran. We removed it from the blog as soon as we saw it. Unfortunately, it takes only seconds for Internet publications to spread. We dropped the ball here."

Indeed, removing content from the Internet is easier said than done. The flaw is now known and, for those in the security community who missed it, the withdrawn post has been mirrored.

So all that's left for those using vulnerable versions of DNS software is to patch.

If they haven't already, the world's cybercriminals soon will be scanning for vulnerable sites, cloning them, adding malware, and then redirecting every would-be visitor to their trap. Or perhaps they'll just decide they'd like to receive all your e-mail.

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