The Internet company has run its own free public Domain Name System (DNS) lookup service, called Public DNS, since 2009. DNS lookups are required to translate a domain name, such as www.idg.com, into an IP address that can be called into a browser.
But DNS systems can be tampered with by hackers. In an attack called "cache poisoning," a DNS server is hacked and modified so that a user looking for www.idg.com is directed to a different website.
ISPs and other network operators have been slowly implementing DNS Security Extensions (DNSSEC), which uses public key cryptography to digitally "sign" the DNS records for websites.
DNSSEC requires a fair amount of work to implement. Domain owners have to ensure their sites are digitally signed. About one-third of top-level domains are signed, but most second-level domains are not, according to Google. ISPs and other network providers must also configure their systems.
Google said it is now checking the digital signatures on DNSSEC-formatted messages, an important step in ensuring correct DNS queries.
"Previously, we accepted and forwarded DNSSEC-formatted messages but did not perform validation," wrote Yunhong Gu, team lead for Google Public DNS. "With this new security feature, we can better protect people from DNS-based attacks and make DNS more secure overall by identifying and rejecting invalid responses from DNSSEC-protected domains."
Google's technical pages on DNSSEC state that if it cannot validate a domain, it will return an error response. But if a very popular domain is failing to validate, it may exclude the site from its blacklist until the problem is fixed.
Google's Public DNS answers more than 130 billion queries from more than 70 million IP addresses per day, Gu wrote. Only 7 percent of those queries request DNSSEC information, however.
"Overall, DNSSEC is still at an early stage and we hope that our support will help expedite its deployment," Gu wrote.
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