In addition to being a fully functional firewall solution, ISA Server 2004 contains a host of other security and productivity features. ISA Server 2004 is often deployed for other non-firewall tasks such as Virtual Private Network (VPN) access, web caching, and Intrusion Detection. Taking it one step further, a slew of dedicated ISA hardware devices has become available from various manufacturers. An understanding of what these types of capabilities are and how they can best be utilized is key.
Allowing for More Intelligent Remote Access with Virtual Private Networks (VPNs)
In addition to having robust firewall capabilities, ISA Server 2004 is also a fully capable Virtua---l Private Network (VPN) solution. Built into the functionality of the product, VPN capabilities allow trusted users that exist outside a network to authenticate with the ISA Server and gain elevated access to internal network resources. In addition to authenticating against Active Directory domains, ISA Server 2004 can utilize RADIUS (Remote Authentication Dial-In User Service) to authenticate users. This capability opens up a range of new architectural capabilities with ISA because the ISA server no longer is required to be a domain member to provide authentication between users. In addition, Internet Authentication Service (IAS) can be used to enable authentication between multiple domains that do not have trust relationships in place, as illustrated in Figure 1.1.
Figure 1.1. Utilizing Virtual Private Networks with ISA Server 2004.
An added advantage to the Virtual Private Network support in ISA Server 2004 is the capability to treat VPN users as a separate network. This allows for a more granular policy control. For example, ISA can be configured to allow only authenticated VPN users to access an Exchange Server. Another function of ISA VPNs is to quarantine VPN clients that do not conform to an organization's security requirements into a restricted network in ISA that has access to only a small range of predetermined services.
ISA Server 2004 supports both Point to Point Tunneling Protocol (PPTP) and Layer 2 Tunneling Protocol (L2TP) for VPN Connections.
For more information on how to set up, configure, and manage Virtual Private Networks with ISA Server 2004, refer to Chapters 9, "Enabling Client Remote Access with ISA Server 2004 Virtual Private Networks (VPNs)," and 10, "Extending ISA Server 2004 to Branch Offices with Site-to-Site VPNs."
Using Web Caching to Improve and Control Web Browsing
The "acceleration" portion of the Internet Security and Acceleration product refers to ISA Server's capability to act as a proxy for network clients, caching commonly-used web sites and their associated graphics, text, and media, and serving them up to end users more quickly than if they had to access the content across the Internet. An additional benefit to this approach is the fact that all outbound web and FTP traffic is then scanned by ISA for threats, exploits, and restricted content. ISA has long been a product of choice for those seeking web caching capabilities. In fact, the previous iteration of the product, Microsoft Proxy Server, was primarily used for that capability by itself in many organizations. ISA Server 2004 caching builds upon this success by further improving the system's caching capabilities.
Utilizing the caching capabilities of ISA Server 2004 is a straightforward and easy-to-deploy method of getting more bandwidth out of an Internet connection. In addition to the capability to cache requests made to web and FTP sites, ISA Server also provides for the capacity to provide commonly-used content from web sites for caching by downloading it on a regular basis. Content download rules can be set up easily to update the cache on a regular basis for sites that administrators designate. This concept can further improve the speed and reliability of web and FTP browsing.
For more information on setting up and configuring ISA Server 2004 to act as a web caching solution, refer to Chapter 8, "Deploying ISA Server 2004 as a Content Caching Server."
Reducing Setup and Configuration Time with an ISA Server 2004 Hardware Solution
One of the complaints with previous versions of the ISA Server product was the fact that it acted in many ways like a traditional server application. It was installed on a base Windows operating system that would subsequently need to be manually secured by a local administrator. This manual securing of the infrastructure on a device touted as a security solution caused many organizations to shy away from deploying it into their environment. In some cases, specific functionality that was offered by ISA Server but not offered by other firewall solutions was passed over in favor of more "traditional" firewalls, which did not require an operating system setup and security process.
To address this concern, Microsoft worked closely with several hardware vendors to offer pre-built and pre-hardened ISA Server 2004 Hardware Appliances. These servers look and feel like traditional firewalls and come pre-built with multiple NICs, quick-restore CDs, and a pre-secured Windows Server 2003 Operating System installed. Many of the ISA servers deployed utilize these hardware devices, and their popularity is subsequently increasing.
The list of hardware vendors offering these dedicated ISA Server 2004 Servers is increasing at a steady pace. Some of the vendors engaged with Microsoft in this program include the following:
There are many advantages to deploying an ISA Server solution using a dedicated hardware device. Installation time is greatly reduced, recovery is simplified, and many of these devices offer specialized functionality, such as specialized VPN appliances, caching servers, and enhanced intrusion detection capabilities.
Reducing Administrative Overhead and Potential for Errors with Simplified Management Tools
A major source of security breaches on all firewalls and security solutions comes down to simple misconfiguration of those devices by administrators. A robust, secure firewall solution becomes nothing more than a router if an administrator accidentally opens it up to all traffic. This concept is often glossed over during a security design process, but it is stunning how often simple typos or misconfigurations result in security breaches.
ISA Server 2004 sports a greatly simplified and easy-to-understand set of management tools that reduce the chance of security breaches through misconfiguration. Functionality is not sacrificed for the sake of simplicity, however, and ISA's simplified Management console, shown in Figure 1.2, allows for a high degree of customization and functionality while simplifying the method in which this functionality is displayed.
Figure 1.2. Using the ISA Server 2004 Management Console.
One of the most common methods hackers use to breach security is to take advantage of a misconfigured firewall. This was one of the main reasons that the ISA tools were simplified and the wizards streamlined, to reduce the chance that an overly complex interface would result in a security breach.
For more information about the ISA tools and how to effectively use them, refer to Chapter 3, "Exploring ISA Server 2004 Tools and Concepts."
Preserving Investment in Existing Security Solutions
One of the common misperceptions about ISA Server 2004 is that it is an "all or nothing" security solution. For example, it was thought that the goal of ISA was to replace other firewall or security devices with Microsoft-only devices. Subsequently, many Security Administrators were hesitant to consider deploying ISA, seeing it as a potential threat to existing firewalls and technologies. The reality of modern ISA deployments, however, is that they are most commonly deployed as an additional layer of security for an organization, not as a replacement for other security layers. For example, many ISA Servers are being deployed as reverse-proxy devices that sit in the DMZ network of an existing firewall solution. As organizations have begun to realize that they do not need to put all their proverbial eggs in Microsoft's basket to be able to utilize some of ISA's enhanced functionality, many of the arguments against deploying ISA have become moot.
The real key to ISA's success lies within its flexibility and its capability to adapt to different security roles within an organization. For smaller organizations that require a complete firewall solution, it delivers. For other larger organizations that are simply looking to secure their Outlook Web Access (OWA) traffic from the Internet, it delivers as well. The different hats that ISA wears are numerous: VPN Server, Web Proxy, Application-Layer Filter, RPC Filter for WAN Segment Traffic, Intrusion-Detection Server, and many more. The capability of ISA to integrate and work with existing security solutions enables organizations to preserve their existing investment in security solutions.
For more information on deploying ISA as an additional security layer to an existing third-party security environment, see Chapter 7, "Deploying ISA Server as a Reverse Proxy into an Existing Firewall DMZ."