IIS 6 on Windows Server 2003 represented a major security improvement over IIS 5, with a redesigned architecture that runs worker processes under low-privilege accounts by default. However, proper hardening is still essential to protect your web server from the constant barrage of attacks targeting internet-facing services.
Application Pool Isolation and Permissions
Create separate application pools for each website or web application, each running under a unique service account with minimal permissions. This isolation ensures that a compromise of one application cannot directly affect others on the same server. Configure the application pool identity to have only the specific file system and registry permissions required by the application.
Remove or disable all IIS components that are not required. Uninstall WebDAV, FTP, and SMTP services if they are not in use. Disable unused ISAPI extensions and web service extensions through the IIS Manager. Each enabled component expands the attack surface and represents a potential vulnerability.
Enable IIS logging with W3C Extended format and include all available fields. Ship these logs to your centralized log management system for analysis. Regularly review 4xx and 5xx error patterns to identify scanning and attack attempts. Implement URLScan as an additional layer of defense to block malformed URLs and common attack patterns before they reach your application code.