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## Seven Domains of a Typical IT Infrastructure No aspect of an IT infrastructure is without risk, nor is it immune to the scrutiny of a hacker. **Risk** is the likelihood that a threat will take advantage of a vulnerability. When designing and implementing network security, you need to analyze eve...

## Seven Domains of a Typical IT Infrastructure No aspect of an IT infrastructure is without risk, nor is it immune to the scrutiny of a hacker. **Risk** is the likelihood that a threat will take advantage of a vulnerability. When designing and implementing network security, you need to analyze every one of the seven **domains** of a typical IT infrastructure (**FIGURE 1-2**) for potential vulnerabilities and weaknesses. Security measures must be detailed, focused, and exhaustive. You must consider every possible avenue of attack; assess risk; and if the risk is sufficient, apply a **countermeasure**. Failing to do so will leave an open pathway for a hacker. A hacker needs only one crack in your defenses to begin chipping away at the security of the entire network. ### Network Security, Firewalls, and VPNs The seven domains of a typical IT infrastructure are: * **User Domain** * **Workstation Domain** * **LAN Domain** * Server * Hub * **LAN-to-WAN Domain** * **WAN Domain** * Firewall * **Remote Access Domain** * **System/Application Domain** * Mainframe * Application and Web Servers Each of the seven domains of a typical IT infrastructure has unique aspects that need security improvements. The following sections describe important foundational network security issues related to the seven domains.