In addition to the enhanced features in ISA Server 2000, ISA Server 2004 introduced the following new features:
Multiple network support and per-network policies ISA Server 2004 introduced the capability to set up and secure ISA between multiple networks. For example, you can set up ISA to act as a firewall between the Internet, an Internal network, a perimeter (DMZ) network, a wireless access network, a VPN clients network, and many more. In addition, you can configure unique policies between each network, such as restricting traffic to a DMZ network or securing RPC traffic across WAN segments. For more information on this feature set, see Chapter 5, "Deploying ISA Server 2004 as a Firewall."
Support for complex and customizable protocols In addition to including a wide array of known protocol support for rules, ISA Server 2004 includes support for custom protocols. These protocols can be defined and specific filters can be created to scan for defined attack patterns in the custom traffic.
New server and OWA publishing rules ISA Server 2004 includes a vast assortment of server publishing rules, including sophisticated OWA publishing rules that utilize advanced functionality such as forms-based authentication and reverse-proxy capabilities. For additional reading on these features, see Chapter 12, "Securing Outlook Web Access (OWA) Traffic."
Remote Procedure Call (RPC) filtering support Of particular note in ISA Server 2004 was the addition of RPC filtering support, which enables an administrator to specify what type of RPC traffic will be allowed from one network to another. For example, a rule could be set up to allow only MAPI Exchange access or Active Directory replication traffic across segments, while blocking other RPC access, such as the kind that spawns attacks and exploits. For more information on RPC filtering, see Chapter 15, "Securing RPC Traffic."
End-to-end secure web publishing capabilities The web publishing rules improved in ISA Server 2004 allow for end-to-end securing of Secure Sockets Layer (SSL) encrypted web traffic from client to ISA server, and then back to web server. When the traffic is decrypted at the ISA server, it can be inspected for viruses and HTTP exploits. The traffic is then re-encrypted before being sent to the web server.
RADIUS and SecurID authentication support In addition to supporting Active Directory authentication, ISA Server 2004 now supports authentication natively against a RADIUS or RSA SecurID authentication infrastructure. This enables an ISA server to be a member of a workgroup, as opposed to a domain member.
Stateful inspection for VPN connections In this version of ISA Server, all traffic that passes through ISA is inspected for Application-layer attacks (stateful inspection). This includes VPN connections as well.
VPN quarantine control features ISA Server 2004 introduces the capability to provide granular control to VPN clients by enabling administrators to restrict new VPN connections to a separate quarantine network. This network can have strict access restrictions placed on it. In this model, VPN users are not moved into the regular VPN users network until it can be established that they satisfy certain criteria, such as the installation of virus-scanning software.
Enhanced monitoring, logging, and reporting ISA Server 2004 includes superb reporting, monitoring, and logging capabilities, including capabilities to write logs to a SQL-desktop version (MSDE) database. ISA can be configured to automatically generate rich reports for client web access, security events, protocol utilization, and much more. Monitoring of ISA is further enhanced with the use of the ISA Management Pack for Microsoft Operations Manager (MOM) 2000/2005. For more information on monitoring ISA Server, refer to Chapter 19, "Monitoring, Troubleshooting, and Intrusion Detection with ISA Server 2004."
The wide variety of features included in ISA Server 2004 makes it very versatile, and it can be deployed to take advantage of one, two, or multiple functions. For example, ISA could be deployed as a full-function firewall, allowing VPN access and web caching. Or it could be deployed simply to filter RPC connections between network segments. An added advantage to this flexibility is the fact that only those functions that are required are turned on. This reduces the surface area that is exposed to attack, reducing the overall threat.
Choosing the ISA Server 2004 Operating System
It is highly recommended that you install and deploy ISA Server 2004 servers on the Windows Server 2003 platform. Improvements in reliability, functionality, and, most importantly, security dictate this. That said, it is possible to install ISA Server 2004 on a Windows 2000 platform, but there are very few practical reasons to do this.
It is important to note that because the ISA Server holds a very important security role, it is essential that you patch the operating system with the critical updates Microsoft releases. This includes the highly recommended Service Pack 1 for Windows Server 2003, and Service Pack 1 for ISA Server 2004, which both introduce advanced security and functionality. For more information on updating ISA Server and Windows with the latest in security and updates, see Chapter 2, "Installing ISA Server 2004."
Both Service Pack 1 for Windows Server 2003 and Service Pack 1 for ISA Server 2004 were released after the general release of the standard version of ISA Server 2004. If ISA Server 2004 is already deployed without these Service Packs, it is recommended that you test them out thoroughly in a test environment before deploying them; the changes and enhancements made to them are significant.
Choosing Between ISA Server 2004 Enterprise or Standard Editions
Unlike many other Microsoft products, ISA Server 2004 was released in two stages. The first stage released the Standard version of the product in mid-2004; whereas, the second stage released the Enterprise version of the product in early 2005. Each version offers different functionality, with the Standard version of the product geared toward small and mid-sized organizations, and the Enterprise version designed for medium to large organizations. The Enterprise version of the software includes all the functionality of the Standard edition, but with the addition of the following:
Array Capabilities ISA Server 2004 Enterprise edition includes the capability to create arrays, which allow multiple servers connected to the same networks to act in tandem to process firewall, VPN, and cache requests. These arrays use the Cache Array Routing Protocol (CARP) to communicate changes and topology information.
Integrated Network Load Balancing (NLB) In addition to the general NLB support provided by the Standard version, the Enterprise version of ISA Server includes advanced integrated support for NLB, allowing an administrator to make changes and manage NLB directly from the ISA Management console.
ADAM Centralized Storage A huge improvement over ISA Server 2000 Enterprise edition is the added capability for Enterprise Configuration information to be stored in a separate instance of Active Directory in Application Mode (ADAM), rather than in the internal Active Directory forest schema. This enables the external-facing ISA Enterprise servers to maintain their configuration in an isolated environment, without unnecessarily exposing internal Active Directory services to attack.
Centralized Management and Monitoring ISA Server Enterprise edition allows for management of a highly scalable ISA solution, with multiple ISA arrays in multiple locations. This allows for centralized management of a complex network infrastructure.
For more information on the advanced capabilities of the Enterprise edition of ISA Server 2004, refer to Chapter 6, "Deploying ISA Server Arrays with ISA Server 2004 Enterprise Edition."