If you are working on a project that is secret what is the most secure way of using PDMW to look after the CAD files?

I guess that one can set up access rights for a selected number of users and set everyone else to have no access. That's fine but what if you don't want anyone outside of the project to know that it even exists? If I hide the project from my SW seat does that hide the project from everyone else as well or just me?

Any other security tips would be welcome.