Permanent fix needed for DNS security issues, Kaminsky warns

Researcher who found cache-poisoning flaw says time has come for DNSSEC technology

Seven months after the disclosure of a fundamental design flaw in the Domain Name System protocol that was discovered by security researcher Dan Kaminsky, industry-wide efforts to address the DNS problem have made considerable headway, according to Kaminsky.

Even so, Kaminsky - who works at security services firm IOActive - said this week that the time may have come for IT vendors and users to consider broad adoption of the more permanent security protections offered by DNS Security Extensions, or DNSSEC, technology.

DNSSEC is designed to make the Internet safer by providing a better method of authenticating and protecting DNS data from cache poisoning attacks - such as the one Kaminsky found - and other security threats. The technology is being vigorously pushed by the federal government on its networks, but many companies have been hesitant about deploying DNSSEC because of its complexity - which includes requiring changes to the DNS protocol itself.

"DNSSEC as an implementation issue remains terrifying," Kaminsky said in an interview after speaking at the Black Hat DC 2009 conference. "There are so many things administrators are supposed to do." As a result, many aren't even trying - leading to a very low adoption rate, he said.

Nevertheless, Kaminsky contended that the inherent security weaknesses in DNS make a strong case for adopting DNSSEC. What the security industry needs to focus on now, he added, is making DNSSEC no harder to implement than deploying the so-called source port randomization fixes for the DNS cache-poisoning flaw was.

"I'm not saying source port randomization was easy," he noted. But once the fixes were implemented, systems administrators didn't have to do anything else to protect their DNS servers against the cache-poisoning flaw, according to Kaminsky. "Once you did it," he said, "you were done."

Kaminsky said the patching efforts launched after he discovered the DNS flaw have resulted in all of the Internet's top-level domains as well as large carrier networks and ISPs being protected against attacks. Given that security researchers originally estimated it would take up to a year for a majority of DNS servers to be patched, "we are more than satisfied" with the progress, he said.

But nearly one-third of the estimated 200,000 DNS servers worldwide still remain unprotected against the cache-poisoning threat and need to be patched as soon as possible, Kaminsky said, adding that many of them are being attacked on a daily basis. "We are seeing attacks where people are redirecting major sites to places where they shouldn't be going," he said. "It's happening right now."

The cache-poisoning flaw was publicly disclosed last July, several months after it was discovered by Kaminsky, who first notified IT vendors to give them time to develop a fix. When he finally detailed the vulnerability, Kaminsky said it existed at the DNS protocol level and was so ubiquitous that virtually every domain name server resolving IP addresses on the Internet was vulnerable to attack. The flaw could be used by attackers to redirect Web traffic and e-mails to systems under their control.

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Jaikumar Vijayan

Computerworld
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