Security Groups Warn of DNS Hole Fix expected today for flaw in common domain name management software.

Stephen Lawson, IDG News Service Monday, January 29, 2001

A vulnerability recently discovered in the software used in most Domain Name System (DNS) servers may be the most serious security threat yet found on the Internet, allowing hackers effectively to shut down ISPs and corporate Web servers as well as steal confidential data.

The flaw is in two widely used versions of Berkeley Internet Name Domain (BIND), distributed free by the Internet Software Consortium (ISC). It could be exploited immediately by unscrupulous programmers if they can write a program to take advantage of it, says Jim Magdych, security research manager at the Computer Vulnerability Emergency Response Team (COVERT) at PGP Security, a Network Associates business. Developing this might take only a few days, he says.

A fix is in the works for release this week, say COVERT and ISC, along with Carnegie-Mellon University's Computer Emergency Response Team (CERT) Coordination Center. They will post the fix on ISC's Web page. The flaw was discovered a few weeks ago, Magdych says.

"If this just showed up in the wild, it could have a pretty serious impact on the Internet at large," Magdych says.

The vulnerability exists in versions 4 and 8 of BIND, the software used in "the vast majority" of DNS servers, though not in the recently released version 9, Magdych says.

Significant Vulnerability DNS servers translate the commands used to access Internet resources, such as Web URLs (Universal Resource Locators) and e-mail addresses, into numbered IP (Internet Protocol) addresses. The TSig (Transaction Signatures) vulnerability lets hackers take control of DNS servers and command them to redirect or block Internet requests sent to them.

A TSig attack could have effects similar to those of the denial-of-service attacks that kept users from reaching Microsoft Web sites last week, or even more serious effects, Magdych says. For example, hackers could take over a financial Web site, recreate the site's login screen, and direct customer names and passwords to a server where they could be stolen.

Skilled hackers who break into corporate DNS servers could block or redirect e-mail and even sabotage access to corporate databases over Internet-based company intranets.

"This is probably the most significant vulnerability to date in BIND," he says. "It's really important that everyone who's affected by this either applies the patch or upgrades to BIND 9."

All hackers will need to do is write a program that sends certain messages as requests to DNS servers. The messages would be interpreted as commands that would open up the server to exploitation.

Just a Matter of Time Although the vulnerability is a subtle one, some hackers could act on it quickly if aware of it, Magdych says.

"When a new vulnerability is discovered, it's just a matter of time before someone develops a program to exploit that vulnerability. Those exploits are then distributed by the community of crackers," or unscrupulous hackers, Magdych says.

"It's certainly not going to be something that takes months. Among our adversaries there are some very talented individuals," he adds.

Installing the patch to BIND versions 4 and 8 probably would require a few hours or more, depending on the number of DNS servers in the network, Magdych says. ISPs and corporations should not jump the gun and shut their DNS servers down cold unless an exploitation program is found in the wild, he adds.

http://www.pcworld.com/news/article/0,aid,39542,00.asp

-- Martin Thompson (mthom1927@aol.com), March 18, 2001