Question : Block access to a single website - Software Resttriction Policies

Can I block acess to a single website (internal site) for a specific OU in the Active Dir? Maybe using software restriction policies?

Staff can access site - http://xxx.webserver, Students can not

Thanks

Answer : Block access to a single website - Software Resttriction Policies

Why not put authentication on the site, either file level using groups or AD authentication?