Windows 7: Hash banning programs ?

hello
im running a few servers on win server 2008
same as win7 im told

I rent out RDP slots
and having a lot of trouble with people abusing the system
mostly doing DDOS attack and encoding programs

I had someone setup a hash ban on one server and it worked really well
when trying to run the bad program we would get a popup saying (blocked by group policy)
I keep asking her to teach me how to do that but im not getting any response
so I thought id ask here

never mind
the resons she wasn't responding is cause she was making an automated vr
I just dropp the file I want banned in a fold and run the bat file