PCI DSS Requirement 5

This is one area that NAC vendors are likely to latch onto, however ask them how they will give you NAC functionality, while securing and encrypting things on the network without a massive hardware footprint or IOS upgrade... TNT can

5.1 Deploy anti-virus software on all systems commonly affected by viruses (particularly personal computers and servers) Note: Systems commonly affected by viruses typically do not include UNIX-based operating systems or mainframes. TNT will insure that the software is active, when the last scan was, tell you about any issues, and if policy is configured to quarantine a machine that is dirty, it knocks it into a quarantine zone.
5.1.1 Ensure that anti-virus programs are capable of detecting, removing, and protecting against other forms of malicious software, including spyware and adware. TNT’s NAC alternative does this by insuring that the software is on, and will synchronize with a real time database of known worms, bots, and other malware
5.2 Ensure that all anti-virus mechanisms are current, actively running, and capable of generating audit logs TNT has the ability to tell admins whether or not the mechanisms are not only up to date but active, and quarantining the device until it is compliant