Risk of net attack rises

Cisco dominates the router market

The internet could come under attack from malicious hackers, warn experts, after details of a software flaw in some of the net's core components were released.

The problem in Cisco routers that decides how and where to send internet traffic was revealed late on Wednesday, but so far there have no reports of any problems.

But this could change now details of how to launch an attack on the equipment have been posted on a mailing list, said the net security watchdog, the Computer Emergency Response Team (Cert).

The fears of interruptions to net traffic are due to the popularity of Cisco routers which are so prevalent on the internet.

Emergency upgrades

The danger to the networking gear is due to the way the Cisco equipment deals with some internet data.

We believe it is likely that intruders will begin using this or other exploits to cause service outages Computer Emergency Response Team advisory

By sending a special sequence of data, a malicious hacker could trick a Cisco router into believing it was full, causing it to crash.

Technicians at internet service providers have been rushing to plug the hole, which in theory could bring net traffic via their networks to a halt.

Many of the big internet service providers (ISPs) have already taken emergency action to update the software with a patch released by Cisco.

But the fear is that smaller ISPs with few support staff could still be exposed.

"This exploit allows an attacker to interrupt the normal operation of a vulnerable device," said Cert in an advisory.

"We believe it is likely that intruders will begin using this or other exploits to cause service outages."

Cisco has released a workaround the problem, as well as a free patch to fix the flaw in its widely used Internetworking Operating System.

The San Jose company is the world's largest supplier of router equipment. Analysts Gartner estimate that the company has 55% of the service provider router market.