Extreme Networks has introduced new rules for its Sentriant security appliances for VoIP technologies that were added to ward off worm outbreaks, denial-of-service (DoS) attacks and other threats to data networks. Such attacks are not yet common in VoIP, but the 2007 book, Hacking VoIP Exposed, Voice Over IP Security Secrets and Solutions, by David Endler and Mark Collier, details the specific susceptibilities of VoIP and has brought the potential threats to the attention of VoIP vendors and users alike. Introduced in March 2008, the rules enable the newest Sentriant appliances to watch for intruders attempting to seize IP phones by impersonating call servers. The rules also protect against attacks on communications and media gateways. The security improvements made to Sentriant are due to a series of new rules that track network traffic activity between IP phones and call servers. With an atypical number of network anomalies, the rules launch a number of protections, including the Address Resolution Protocol to redirect attack packets away from intended targets, the cloaking threat mitigation technique and others. Extreme Networks created the rules in response to customers who wanted to develop their own rules via the companys APIs and the devices security monitoring features. Following this first release, Extreme plans to continue developing rules for the Sentriant appliance.