mod_auth_vas is an authentication and authorization module for use with the Apache web server. Derivatives including IBM HTTP Server and Oracle HTTP Server are also supported. The module uses Quest Authentication Services (QAS) to implement the HTTP SPNEGO protocol which provides passwordless authentication on web servers with optional fallback to password authentication. In effect, mod_auth_vas allows the Apache web server to perform Windows Integrated Authentication (single sign-on). Browsers that can authenticate using SPNEGO automatically (without prompting for a password) include Internet Explorer, Firefox, Safari and Google Chrome