ISA Server 2006 is commonly deployed for its reverse-proxy capabilities, particularly in its
ability to secure web servers and Exchange Outlook Web Access (OWA). Through reverse
proxy, clients on the Internet are directed to the external IP address of the ISA server,
which they think is the actual server for the services that they require. In reality, ISA
performs Network Address Translation (NAT), scans the traffic for exploits and threats at
the Application layer, and forwards the traffic back to the server. This greatly reduces the
threat posed by having servers and services exposed to the Internet.
Server publishing rules in ISA Server allow for advanced services securing SQL servers,
Exchange servers, Web servers, SharePoint sites, RPC services, and many other predefined
options. For more information on configuring and using server publishing rules,
see Chapter 5.
Understanding System Policy Rules and the System Policy Editor
System policies are often misunderstood or not taken into consideration, but are a fundamental
component to every ISA installation. System policies are essentially a default set of
firewall policies that allow the ISA server to perform various system functions.
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