ISA Server is a complete solution by Microsoft for providing an access point between the Internet and the corporate internal network. It can operate as a firewall, limiting access to and from the internal organization network. ISA Server provides a proxy and caching server enabling access to resources on the Internet to internal network clients. It also acts as a VPN endpoint, and provide Internet Access for client systems in a Business Networking environment.
ISA server provides advanced protection for networks. It operates as a firewall and examines every packet flowing through it providing a good protection from hackers, viruses etc.It supports multiple networks and enables the configuration of network and firewall rules that filter the flow of traffic between all networks.
All firewall rules can be viewed and modified in a single location by using ISA Server management console making it easier to avoid security breaches due to firewall misconfiguration. It can also be integrated with Active Directory infrastructure to provide authentication. ISA provides fast and secure access to corporate applications and data such as MS Exchange Server and Internal Web Servers.
ISA 2006 introduces a variety of improvements upon the previous version, ISA 2004, including support for authentication via Secure LDAP, (LDAPS) to multiple LDAPS providers or Active Directory forests, integrated support for Exchange 2007 (also backported to ISA 2004), support for publishing Microsoft SharePoint, Single sign-on, Cross-Array Link Translation, Web Publishing Load Balancing (with cookie-based affinity for Integrated NLBS) as well as variety of improvements to wizards such as a Branch Office VPN Connection Wizard, improved certificate management, and Link translation. ISA Server 2006 is only available in a 32 bit version. It also does not work on Windows Server 2008 due to the extensive changes to the networking stack.