How NAC Works
There are two main parts to NAC, the first being a piece of software that runs on the client (or, more generally, "endpoint," because it could be a server, too, or something unconventional) called the Cisco Trust Agent or CTA. At the back end is a policy management system called the Cisco Access Control Server (ACS). Cisco gives away the CTA, and the ACS is already widely used for various 802.1x-based authentication functions. Cisco approached the big client security companies (Symantec Corp., Trend Micro Inc., Network Associates Inc.s McAfee Security) and got their cooperation. These three probably constitute more than 90 percent of the corporate antivirus market.King says Cisco could open up the APIs for communication between the client software and the CTA, as well as the APIs between the ACS and other vendors policy managers, and that would be great. If they opened up the protocols between the CTA and the ACS, that would be even better, although I can see why Cisco would hesitate to do it, since it would open up the possibility of third-party implementations of NAC. Consider that if NAC caught on, there would be a lot of pressure for a built-in Linux client; lots of people would want this to be a source code version. Cisco is still deciding on how to proceed; I think it would do well to be aggressive in opening it up. It would accelerate general acceptance of the system, and that would only be good for Cisco, which plans to put NAC in everything from routers and switches to wireless access points. Eventually Id even like to see ISPs implement something like this. Id pay extra for an ISP that did have such rules, but I wouldnt put any money down that they will. ISPs seem loath to lose even their infected customers. Its true that new attacks come along, and NAC wouldnt be able to stop most of them, but the vast majority of the problem out there comes from old attacks, or at least from those detected by the current definitions of any major AV product. With NAC or something like it in place, networks will be able to defend themselves against users who dont know enough to protect themselves. Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983. Check out eWEEK.coms Security Center at http://security.eweek.com for security news, views and analysis. Be sure to add our eWEEK.com security news feed to your RSS newsreader or My Yahoo page:
More from Larry Seltzer
The protocol between the CTA and client software allows it to check the status not only of the antivirus software and definitions, but also firewalls and the operating system version and patches. Depending on what is found, the administrator can set policies to lock out the user or place them in a restrictive environment.