Kaminsky: DNS Vulnerability Will Affect Email, Internal Systems, Too

LAS VEGAS – Black Hat 2008 – After almost a month of holding back, security researcher Dan Kaminsky took off the gloves and delivered the full impact of his newly discovered Domain Name Server vulnerability to an audience of more than 2,000 security experts here.

The presentation was the end of a long wait for many security researchers and professionals, who were first tipped off to the threat following an unprecedented, simultaneous patch release conducted by multiple vendors in early July. Kaminsky warned the industry of the flaw when the patch was released, but declined to give details, citing a desire to buy more time for vendors and users to implement the fix. (See Vendors Issue Massive Simultaneous Patch for Common Internet Flaw.)

Today's session didn't reveal anything new about the nature of the flaw, which essentially allows attackers to exploit the DNS design to quickly guess the transaction ID of an address query and potentially re-route the user to an unexpected domain. (See Details, Exploits of Web-Wide DNS Vulnerability Revealed.)

However, Kaminsky went into vivid detail on the ubiquity of the DNS lookup process, and how it might be exploited in the wild. And the potential for attacks is broader than most previous reports indicated.

While most early discussions focused on Web surfing and the potential hijacking of users' browser sessions, Kaminsky today pointed out that DNS address queries are embedded in a wide variety of applications and services that had not entered the conversation previously.

"The Internet is more than just the Web," Kaminsky said. "HTTP is used in more than just the browser."

Most email systems, for example, contain DNS lookup capabilities and even their own name servers, Kaminsky observed. "Email servers are awesome at doing DNS lookups," he said. "They will do a DNS lookup for any reason at all. And your spam filter will not stop this problem."

Many enterprises also believe that their internal DNS environments will not be vulnerable, Kaminsky observed. But many internal environments also work with external DNS servers, and even if they didn't, most internal environments are also connected to DNS servers used by customers or suppliers, he noted.

The DNS flaw can affect any system that uses the Internet, including older applications such as FTP that are still widely used, Kaminsky noted. Back-end IT systems such as Telnet, SNMP, authentication servers (such as Radius), backup and restoral systems, and even service-oriented architecture (SOA) environments all use DNS, and could be subject to attack via the newly discovered flaw.

Traditional Web security technologies like Secure Sockets Layer (SSL) encryption also will be largely ineffective in preventing attacks that exploit the DNS bug, Kaminsky said. Most Websites do not fully enforce the use of SSL, and most sites offer a "forgot your password?" option that essentially provides a "skeleton key" that would allow the DNS attacker to bypass many of these Web security tools, he explained.

For now, the best answer continues to be the patch that Kaminsky and a cadre of vendors introduced back on July 8. The patch adds a port randomization factor to the address query, making it much more difficult for hackers to hijack the query than they would with traditional transaction IDs alone, Kaminsky said.

Thus far, about 70 percent of the Fortune 500 has deployed the patch, and another 15 percent has made a deployment but is still wrestling with network address translation problems, Kaminsky said: "Only 15 percent has done nothing, and under the circumstances, that's pretty good."

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