Hewlett-Packard on Friday rolled out a software add-on for its ProLiant servers and HP BladeSystem that shuts down the inside-the-network spread of worms or viruses within milliseconds.

With the catchy name of Virus Throttle, the software eschews the traditional anti-virus technique of comparing possible malicious code against a database of signatures, and instead watches for virus-like behavior and then quarantines the infected machine until an administrator can figure out what's going on.

When malicious code is suspected, Virus Throttle stops its spread by preventing the machine from making network connections. The software then flags the administrator, who can take the appropriate action, such as virus removal or additional investigation.

The faster a virus or worm tries to spread by opening up more and more connections to the network, HP said, the faster Virus Throttle reacts. Typical response time, HP claimed, was within milliseconds.

Virus Throttle comes as part of the new ProLiant Essentials Intelligent Networking Pack, a $149 add-on. The software is also available to users of HP's ProCurve Switch 5300 series, HP's flagship line of at-the-edge network switches. Current owners of the 5300xl can download the software from HP's Web site.