Enterasys Networks late last month unveiled technology to help prevent viruses and worms from making their way onto a network.The company\u2019s Trusted End-System, or TES, checks out each end device as it attempts to connect to a corporate network through Enterasys switches. If a machine doesn\u2019t meet specific security requirements - if it is infected with a virus, for instance - the switch won\u2019t let it connect to the network.TES uses technology from Sygate and Zone Labs, which are Enterasys Secure Networks Certified Partners.Network-based security is important because computers are mobile. Laptop computers can go away from a protected corporate network, get infected, and return. Or visitors can bring their own laptops to a corporate office and end up bringing their infections with them.Cisco and Nortel also have their approaches to this problem. Enterasys touts the immediate availability of TES and the fact that it uses current desktop security software.TES allows network managers to control access at the user and port levels, rather than controlling access for groups or virtual LANs. It uses software agents today, and by the end of the year will add a network-based option by year-end. This second approach will be important for environments where distributing software agents to end points is not feasible, like a university campus with many laptops.Enterasys says it is offering a couple professional service programs to help customers get started with TES. One involves assessing a network and planning migration to TES, another details a phased implementation approach to deploying TES.