Flaw leaves systems susceptible to denial-of-service attacks, service interruptions, and possible break-ins.

The FBI is monitoring "potential vulnerabilities" in computer networks that could leave portions of the Internet open to disruption by hackers, the agency said on Tuesday.

"We're aware of potential vulnerabilities... and to date there have been no confirmed exploitations of these vulnerabilities," said Steven Berry, spokesman for the FBI's National Infrastructure Protection Center.

An advisory disclosing a flaw was issued on Tuesday by the Computer Emergency Response Team at Carnegie Mellon University in Pittsburgh.

It said the flaw leaves systems vulnerable to paralyzing denial-of-service attacks, service interruptions, and possible break-ins. It recommends ways to minimize the vulnerabilities, but says some of the assaults can significantly affect the performance of a computer system.

Homeland Security Director Tom Ridge was informed of the vulnerability as part of his regular briefings on potential security threats, said Ridge spokesman Susan Neely.

The advisory said the vulnerability affects the Simple Network Management Protocol, used for monitoring and managing computer network devices.

Also on Tuesday, the FBI and Secret Service issued guidelines for businesses to use in planning for and responding to computer system attacks and security breaches. The guidelines urge business leaders to establish contacts with law enforcement agencies, and it explains how to report incidents to authorities.