Identifying and Reducing Anonymous Traffic Allowed by Forefront TMG 2010
My recent blog post about altering the SafeSearch enforcement rule in Forefront TMG 2010 to require authentication has sparked some discussion on Twitter and Facebook regarding unauthenticated, anonymous access, particularly to resources located on the public Internet. In a perfect world (ok, my perfect world!), all access to and through the TMG firewall would be fully authenticated. Unfortunately, for a variety of reasons, this isn’t achievable. To start, authenticating all traffic to and through the TMG firewall would necessitate that all clients be configured as explicit web proxy clients. In addition, if non web-based protocols are allowed by firewall policy the Firewall Client would need to be distributed to all clients. While this is ideal if we’re designing a solution on paper, in the real world many administrators don’t have the luxury of forcing proxy configuration or installing the Firewall Client on all their systems. For example, some systems may not be under the administrator’s control or they may be required to support non web-based protocols on platforms other than Windows, for which the Firewall Client is not supported. Also, as veteran ISA and TMG firewall administrators know all too well, there are some applications that simply don’t play nice with an authenticating proxy, even with the Firewall Client installed. Applications that don’t leverage Winsock for network communication or that use IP-based protocols such as ICMP or GRE also prevent us from realizing our goal of authenticating all network traffic through TMG. Windows Update traffic also poses challenges for authenticating all TMG traffic, as the Windows Update service often makes requests to the Internet for updates in the background and perhaps even if there is no interactive user logged on.
Just because out of necessity some traffic has to be allowed through the TMG firewall anonymously doesn’t mean that undertaking an effort to reduce unauthenticated traffic isn’t a worthwhile project. If you’re interested in doing something like this, have a look at the Fastvue blog and read Scott Glew’s excellent article detailing how to use TMG Reporter to identify and reduce unauthenticated traffic on the Forefront TMG 2010 firewall. Not using TMG Reporter? You’re missing out! Download a free evaluation here!