The wide variety of so-called NAC (network access control) products on the market shows a broad range of thinking about policy-based security controls and the management of the network in general, including the end-point devices that connect to the network. Some vendors enforce policies using a client agent, some enforce them in the network, and some even use peers for enforcement. Network-based enforcement itself can take many forms, including dedicated gateway, DHCP manipulation, 802.1x authentication, and port- and VLAN-based enforcement on switches.

In short, there are many ways to skin the NAC cat.

Considering Sophos' extensive background in managing the security of host systems, you might expect its NAC solution to make use of agent-based enforcement, and you'd be right. However, Sophos also took a decidedly open path to the system, allowing for integration with environments using a wide range of anti-virus agents, 802.1x, DHCP, Cisco NAC, and VPN methods of control and enforcement.

Sophos NAC Advanced combines a Windows Server 2003-based policy management server with end-point agents, dissolvable agents, and reporting to deliver a compelling system for Windows-oriented environments. Although Sophos offers anti-virus software for Mac OS X and Linux as well as Windows, this first release of Sophos NAC Advanced is focused strictly on assessment and policy management for Windows end points.

Policy is king

As in my previous reviews of solutions from ConSentry, Enterasys, McAfee, Symantec, and Trend Micro, I looked at the Sophos product's ability to address a set of typical enterprise policies and distinguish the ways in which the product does that. When choosing among NAC solutions, the key is to consider your requirements from within the universe of possible policies, especially in terms of the granularity of both the policies and their enforcement. You will also want to consider how (and how frequently) you want to interact with the system and whether ease of policy creation, policy modification, or reporting are your most vital requirements.

Sophos takes a hierarchical approach to policies. Using a straightforward Web-based GUI, admins create a hierarchy of profiles, with each policy comprising one or more profiles plus the defined outcome for compliant, partially compliant, and noncompliant systems. Sophos allows policies to be run in report-only, remediate, or enforcement mode. This flexibility is especially useful during the introduction of new policies into the system, and provides for a transition as you determine the compliance of the end points in your environment.

You can create profiles for the operating system (at least one of which is required for every policy), applications (including both security components such as anti-virus as well as user applications such as Internet Explorer), and patches for each of them, and assemble them into policies that outline the required OS patch level, anti-virus application and signature currency, and firewall application and settings. The policy definitions also include the resulting access available to the end point and any alerting necessary. In addition, you specify how frequently the agent on each end point will check for updates to the policy, assess and reassess the host system for compliance, and communicate with the reporting system.