Computer security professionals crammed into a Las Vegas ballroom on Wednesday for the first public briefing on an Internet flaw that lets hackers hijack traffic on the World Wide Web.

"There is bunch of weird (stuff) going on out there right now," expert Dan Kaminsky told AFP, confirming that attacks are being launched online despite efforts to conceal and patch the vulnerability in the Internet's foundation.

Kaminsky, the director of IOActive penetration testing, was met with applause and cheers when he stepped to a podium at the premier Black Hat conference to reveal details of an attack that is a boon to ill-willed hackers.

An elite squad of computer industry engineers labored in secret to solve the problem, and released a software "patch" in early July but sought to keep details of the vulnerability hidden until Black Hat to give people time to protect computers from attacks.

The Domain Name System (DNS) flaw was figured out and spread online within two weeks of the patch's release and US telecom giant AT&T was the first confirmed victim of an attack.

Kaminsky said that while businesses are still hustling to protect their Internet traffic, only 15 percent Fortune 500 companies have "done nothing" to defend their computers.

"How do you force a server to 1.badguy.com?" Kaminsky asked rhetorically as he addressed the crowd.

"Oh, let me count the ways. God, it's good to be finally able to talk about this stuff."

Kaminsky stumbled upon the DNS vulnerability about seven months ago and reached out to industry giants to collaborate on a solution.

DNS is used by every computer that links to the Internet and works similar to a telephone system routing calls to proper numbers, in this case the online numerical addresses of websites.

The vulnerability allows "cache poisoning" attacks that tinker with data stored in computer memory caches that relay Internet traffic to its destination.