Patch in Internet's DNS no guarantee against attacks

Patches meant to fix a flaw in the Internet's Domain Name System (DNS) don't completely protect the Web's traffic cop from attack, a Russian research claimed Friday.

The head of the nonprofit that maintains the most commonly used DNS software, however, said there was little to worry about.

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In a blog post, Russian researcher Evgeniy Polyakov said he had created an exploit able to insert bogus routing information into systems running the most-up-to-date version of BIND (Berkeley Internet Name Domain), the popular open source software that runs a majority of the Web's DNS servers.

BIND 9.5.0-P2 was released Aug. 2 as a follow-on to the initial patch issued July 8, the day that researcher Dan Kaminsky announced the DNS flaw and a coordinated patching effort by several vendors, including Internet Systems Consortium Inc. (ISC), which maintains BIND; Microsoft Corp.; and Cisco Systems Inc.

Both the July 8 and Aug. 2 BIND updates added source port randomization in the name server to reduce the likelihood of "cache poisoning," the term used to describe attacks that attempt to reroute users' requests for legitimate sites to fakes created to dupe them into entering confidential information.

Polyakov claimed that his exploit was able to insert rogue instructions into a DNS server running BIND 9.5.0-P2, although it took a pair of attacking PCs connected to the server via a Gigabit Ethernet (GigE) network connection about 10 hours to pull off the attack.

"Attack took about half of the day, i.e. a bit less than 10 hours," Polyakov said on his blog. "So, if you have a GigE LAN, any Trojaned machine can poison your DNS during one night."

Computerworld was not immediately able to verify Polyakov's claims.

Paul Vixie, the president of ISC, said the threat posed by Polyakov's exploit was small potatoes compared to the ease with which attackers can poison the caches of unpatched DNS servers. "While I think it's bad that anybody who can hammer you at GigE speed for ten hours can poison your cache, it's not a threat to the real world the way 11 seconds at 10-megabit was," Vixie said in a message posted Sunday to a BIND mailing list.

"Any DNS server with a host-based firewall can implement a 100% effective mitigation for the Polyakov attack, and it's possible that an upstream/outboard firewall could also be made to do it," Vixie said. "At some point ISC will have to put logic like this into BIND, of course, but protecting against the Polyakov attack is like synflood protection in that it's a rate-limit problem."