The Global.asa file typically stores user session variables and application start profiles. Because the Global.asa file also includes commands that return information to the browser, it's important to secure it. You can fully protect the Global.asa file by using NTFS file permissions.
For More Information Protecting Files, in this chapter, introduces file-level security through NTFS. For more information on securing the Global.asa file, search for "Security Topics for Visual InterDev" and "Securing an ASP Application" in MSDN Library Visual Studio 6.0.