ServerMask for IIS
Broadcasting clues about a Web server via its HTTP header makes it easy for a potential intruder to complete his/her first hacking task: identifying your operating system and Web server. ServerMask 2.2 from Port80 obscures a Windows Web server removing or modifying unnecessary HTTP and SMTP response data, the most obvious signs that you are running IIS. The tool installs easily, is stable and efficient, and is available for a free 30-day trial.