UK government warns on critical web vulnerability

The UK's web security watchdog has issued a warning on a critical web vulnerability just as a US researcher is poised to tell how to hack into it.

US researcher Paul Watson, who discovered the flaw in TCP (transmission control protocol) late last year, is to reveal all tomorrow (Thursday) to an internet security conference in Vancouver.

The technique will allow hackers to knock unprotected computers offline and to broadly disrupt routers and net traffic. The UK National Infrastructure Security Coordination Centre (niscc) issued an advisory on the vulnerability on Tuesday.

It said: "The impact of this vulnerability could allow an attacker to create a Denial of Service condition against existing TCP connections." It added: "The impact of this vulnerability varies by vendor and application, but in some deployment scenarios it is rated critical."

Watson discovered a technique to reliably shut routers down by resetting them remotely. The odds against being able to crack the inter-router codes, basically cracking a rotating number from four billion combinations, were previously estimated as being very high – and would take between four and 142 years to execute.

Watson's technique takes four tries and a couple of seconds. He will reveal this tomorrow in a presentation entitled 'Slipping in the Window: TCP Reset Attacks' at the cansecwest conference which starts today in Vancouver.

The UK warning says that the BGP (boarder gateway protocol) is potentially the most seriously affected by this style of attack and that there is a potential impact on the DNS (domain name system) and SSL (secure socket layer).

Niscc advises users to consult their vendors for patches and solutions to the threat. It has a list of vendors and solutions on its website under advisory 236929.