Summary

Application proxy firewalls can perform a specialized role in managing the security of an enterprise by providing for application layer inspection of the data that is being controlled. This allows application proxies to not only make filtering decisions based on the protocol or port that traffic is using, but by looking at the raw data and making a filtering determination based on the application itself, for example differentiating between malicious and non-malicious web traffic.

Microsoft ISA Server 2004 is a fully featured enterprise class firewall that provides for application filtering of many protocols, while implementing stateful packet inspection for all remaining traffic. It can be used as a standalone perimeter firewall but is particularly effective as the interior firewall in a dual-firewall architecture.

Note

For more information about Microsoft ISA Server 2004, check out Dr. Tom Shinder's Configuring ISA Server 2004 (Syngress, 2004).