Server Folder Access / Security

We have a sub-folder on one of our NT servers that we want to isolate to just 3 people. I’ve tried many options but can’t get it the way I’d like. The problem is that it seems that an unauthorized user can still overide the settings and can get into the folder by right-clicking the unaccessed folder and resetting the permissions, upon which he can then get in.

How can I make sure any unauthorized user can’t somehow takeover the settings (even though they don’t have administrative rights) whether it be changing permissions or by taking ownership

Thanks