DNS Flaw Leaves Major Internet Security Hole

Vendors team up to patch deficiencies in the protocol used by the Domain Name System that can be exploited to poison DNS caches and redirect user traffic on the Internet.

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A number of vendors have teamed up to solve a serious flaw inherent in the Domain Name System that could allow an attacker to redirect Internet traffic.

The flaw in the DNS, an Internet service that translates domain names into IP addresses, was uncovered by security researcher Dan Kaminsky, director of penetration testing for IOActive.

During a press briefing July 8, Kaminsky was mum about specific technical details of the vulnerability, but said the problem has been solved by implementing port randomization. Rather than randomizing on an ID transaction field of 16 bits, it will now randomize using 27 to 30 bits, he said.

According to officials at the ISC (Internet Systems Consortium), the DNS protocol uses the Query ID field to match incoming responses to previously sent queries. The Query ID field is only 16 bits, however, and in the scenario discovered by Kaminsky, that is not random enough to prevent easy exploitation, ISC officials said in a statement.

"It's the kind of a flaw that would allow an attacker to, say ... go after your ISP, and if somebody dialed in, or wanted to go to Google.com, they could redirect them to pretty much any place they wanted," Rich Mogull of security consulting company Securosis said during the briefing.

So far, there have been no attempts to exploit the vulnerability in the wild, according to Kaminsky, who added that more information will be released in the next 30 days to help businesses better protect themselves.

"Design bugs are interesting in that they don't just constrain themselves to an individual company, an individual implementation," Kaminsky explained. "Because the system is behaving exactly like it's supposed to behave, the same bug will show up in vendor after vendor after vendor ... this one flaw that I had found, this one issue I had found, actually affected not just Microsoft, not just ISC BIND, not just Cisco, but everybody."

The flaw was uncovered six months ago. On March 31, 16 researchers from around the world met to come up with a solution to the problem, and agreed to coordinate the release of a patch across all platforms.

"Our primary focus is on DNS servers, because the vulnerability is primarily a server vulnerability," Kaminsky said. "There are scenarios in which not just DNS servers, but all the little clients out there that happened to use DNS, there are scenarios in which those hosts can be vulnerable as well. It's not the focus; they are not universally vulnerable. But there are patches that are out now or may be coming that will handle those clients."