SAN FRANCISCO - Internet security researchers have warned that hackers have caught on to a "critical'' flaw that lets them control traffic on the internet.

An elite squad of computer industry engineers that laboured in secret to solve the problem released a software "patch'' two weeks ago and sought to keep details of the vulnerability hidden for at least a month to give people time to protect computers from attacks.

"We are in a lot of trouble,'' said IOActive security specialist Dan Kaminsky, who stumbled upon the Domain Name System (DNS) vulnerability about six months ago and reached out to industry giants to collaborate on a solution.