Firewall Client for ISA Server can be optionally installed on client computers protected by Microsoft ISA Server. Firewall Client for ISA Server provides enhanced security, application support, and access control for client computers. It provides authentication for Winsock applications that use TCP and UDP, supports complex secondary protocols, and supplies user and application information to the ISA Server logs.
When a client computer running Firewall Client for ISA Server makes a request, the destination is evaluated by the Firewall Client software, and external requests are directed to the ISA Server computer for handling. No specific routing infrastructure is required. Firewall Client sends user information transparently with each request, enabling you to create a firewall policy on the ISA Server computer with rules that use the authentication credentials presented by the client. ISA Server allows you to configure automatic discovery for Firewall client computers, using a WPAD entry in DNS or DHCP to obtain correct Web proxy settings for clients, depending on their location.
For more information about Firewall Client, see Internal Client Concepts in ISA Server and Automatic Discovery in ISA Server at the Microsoft TechNet site.