Hvordan kan jeg tvinge alle brugere ud af et websted?

Som Joe foreslår, kan du skrive et HttpModule for at ugyldiggøre alle cookies, der er til stede før en given DateTime. Hvis du sætter dette i konfigurationsfilen, kan du tilføje/fjerne det, når det er nødvendigt. For eksempel

Web.config:

<appSettings>
  <add key="forcedLogout" value="30-Mar-2011 5:00 pm" />
</appSettings>

<httpModules>
  <add name="LogoutModule" type="MyAssembly.Security.LogoutModule, MyAssembly"/>
</httpModules>

HttpModule i MyAssembly.dll:

public class LogoutModule: IHttpModule
{
    #region IHttpModule Members
    void IHttpModule.Dispose() { }
    void IHttpModule.Init(HttpApplication context)
    {
        context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest);
    }
    #endregion


    /// <summary>
    /// Handle the authentication request and force logouts according to web.config
    /// </summary>
    /// <remarks>See "How To Implement IPrincipal" in MSDN</remarks>
    private void context_AuthenticateRequest(object sender, EventArgs e)
    {
        HttpApplication a = (HttpApplication)sender;
        HttpContext context = a.Context;

        // Extract the forms authentication cookie
        string cookieName = FormsAuthentication.FormsCookieName;
        HttpCookie authCookie = context.Request.Cookies[cookieName];
        DateTime? logoutTime = ConfigurationManager.AppSettings["forcedLogout"] as DateTime?;
        if (authCookie != null && logoutTime != null && authCookie.Expires < logoutTime.Value)
        {
            // Delete the auth cookie and let them start over.
            authCookie.Expires = DateTime.Now.AddDays(-1);
            context.Response.Cookies.Add(authCookie);
            context.Response.Redirect(FormsAuthentication.LoginUrl);
            context.Response.End();
        }
    }
}