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 , 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 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.