In Hollywood, the killer mutant virus always kicks mankind's butt. For security pros, this is one area where life too often imitates art—a single infected laptop can make for a very long night. While the Storm worm made headlines, its main propagation method is through user action. That's defensible. It's automated worms like SQL Slammer and Code Red that are likely to do far more damage when they get into your network, because they can infect any vulnerable computer without end user intervention.
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Welcome to the final entry in our NAC Rolling Review trilogy. We've covered in-band and out-of-band network access control systems, and now we turn to host-based NAC, which aims to solve problems like malware propagation and unauthorized access by adding agents to hosts and controlling access from the source of the problem, rather than in the network or at a perimeter. Vendors tout simple-to-install agents that augment or replace existing security tools. What's more, there are no network changes involved. No re-cabling. Fewer chokepoints and single points of failure. No creating VLANs, subnets, DHCP scopes or 802.1X. That benefit alone will make host-based NAC palatable to companies that just don't want to mess with their network topologies.
Our most recent NAC trend survey showed host-based NAC on par with out-of-band, 51% to 50%, when we asked what changes readers would be willing to make to their networks. In-band is still the NAC architecture of choice, at 65%. In that same survey, we asked about types of activity that require access control. The Top 3 answers: access to the data center (50%), remote access (39%) and branch office access to corporate resources (37%). That sends a strong message that readers want internal access control, and that they have operational power over endpoints—a critical requirement for host-based NAC. Companies for which controlling guest access is crucial should look to an alternate strategy, because installing a permanent agent on an unmanaged node is an iffy proposition at best.
NAC vendors tout worm containment as a top driver. The idea is that assessment during and after network connection will pinpoint infected nodes. The NAC system can then take action, moving the host to a quarantine network or forcing upgrades and cleaning before it's allowed back on the network. The big "if" here is properly detecting infections in the first place—not an easy task because more invasive malware actually disables antivirus and other security software.