One of my customers recently deployed Forefront Protection 2010 for SharePoint to their SharePoint 2010 farm, the installation completed successfully – result! Although we now had a slight problem, each WFE has a non-SharePoint web site created in IIS; this is used purely by their monitoring system to check that IIS is up and running. When browsing to this “test” site the following error was being displayed:
“HTTP Error 500.0 - Internal Server Error - Calling LoadLibraryEx on ISAPI filter "c:\Program Files\Microsoft Forefront Protection for SharePoint\FSSPUsernameFilter.dll" failed
It turns out that during the installation an ISAPI filter named “FSSP Username Filter” is added to all web sites that are registered in IIS. The easiest way to resolve this issue is to remove the ISAPI Filter from any non-SharePoint Web sites.
As I’m lazy and love to automate things I used the following command to do this (replacing Test” with the name of the site to remove the ISAPI Filter from).
Appcmd.exe set config "Test" -section:isapiFilters /-"[name='FSSP Username Filter']" /commit:apphost
The site now renders correctly!