Comcast begins DNS security rollout

First in U.S. to protect customers against Kaminsky-style cache poisoning attacks

Comcast has begun migrating its customers to a new Internet security mechanism that will help protect them from being inadvertently routed to phony Web pages for pharming attacks, identity theft and other scams.

Comcast is the first major ISP in the United States to adopt the new mechanism, which is known as DNS Security Extensions (DNSSEC).

DNSSEC is an emerging Internet standard that prevents hackers from hijacking Web traffic and redirecting it to bogus sites by allowing Web sites to verify their domain names and corresponding IP addresses using digital signatures and public-key encryption.

DNS gets added measure of security starting today

Comcast says all of its business and residential customers will have DNSSEC coverage by March 2011.

"Starting on Monday, we will start migrating customers to the DNSSEC validating servers," says Jason Livingood, executive director of Internet Systems Engineering for Comcast. "We're doing it in a phased approach."

The March 2011 date is significant because that's when VeriSign plans to support DNSSEC for the .com domain that it operates. The Internet's most popular domain, .com has more than 80 million registered names as of September 2010.

The Internet's root servers, which sit at the top of the Internet Domain Name System hierarchy, began supporting DNSSEC on July 15.

DNSSEC also is supported by 55 of the Internet's 294 top-level domains, including the .org domain used by non-profits and the .edu domain used by universities. VeriSign says it will support DNSSEC in the .net domain by year-end.

"We would like to complete our migration of subscribers before the .com [top-level domain] signs," Livingood says.

Comcast began a public trial of DNSSEC in February, announcing at the time that it planned to provide production-quality DNSSEC resolution services to all of its customers by the end of 2011.

Now, having experienced few technical glitches with DNSSEC, Comcast will support the emerging standard several months sooner.

"We've been actively trialing DNSSEC on the public Internet for a little more than two years now…Starting in 2010, we announced the start of our public DNSSEC trials," Livingood says. "All of the operational issues we ran into and any of the technical issues have been sorted out fully in the past couple years."

Comcast's customers won't see any change in their Internet service as a result of the ISP's DNSSEC support. That's because few Internet applications currently support the standard. One exception is the Firefox Web browser, which has a DNSSEC plug-in that shows a user when a Web page they are visiting has been verified or spoofed.

Once a Web site cryptographically signs its domain, Comcast's DNSSEC servers will validate that the Web site's security key is accurate and hasn't been tampered with by a hacker. If the key validation fails, the end user won't be directed to the phony Web site.

DNSSEC "is a fairly technical subject. I don't think it's something that the average customer is aware of," Livingood says. "But some of the large commercial Web sites that are customers are aware of it. We expect very large banks to implement DNSSEC as soon as the associated top-level domain supports it."

In order for DNSSEC to be effective, it must be deployed across the Internet infrastructure from the root server clusters, to the servers that run .com and .net and other top-level domains, and then down to the servers that cache content for individual Web sites. ISPs must support DNSSEC resolution for their customers, and users must have Web browsers and other applications that can validate queries using the standard.

Once it is widely deployed, DNSSEC will prevent cache poisoning attacks, where traffic is redirected from a legitimate Web site to a fake one without the Web site operator or user knowing. Cache poisoning attacks are the result of a serious flaw in the DNS that was disclosed in 2008 by security researcher Dan Kaminsky.

"DNSSEC is a critical thing that needs to be adopted," Livingood says. "It's very exciting that we're the first large ISP in the U.S. that is adopting this for our subscribers."

In a separate announcement last week, Comcast said it has donated $15,000 to a fund run by NLnet Labs that will encourage application developers to support DNSSEC.

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