I assume you are already compiling the database into a mde or..acccde to protect the forms, report, and modules.
It is very difficult, maybe impossible, to keep everyone out of the tables and query in a mde/accde. You can make it difficult.
After compiling a new front end, on the copy that I will deploy I run some lock down code. It runs things like use special keys, disables the shift key bypass, do not display the nave pane/ database window, sets the .Attributes for some objects to hidden. This keeps the users out of the navigation pane/database windows.
I also use force Access into runtime mode if they are not using the Access runtime. This really locks down even if you do not do all the stuff above. I do both so it is as difficult as possible to break in. Runtime mode disables the navigation pane/database windows and all design tools. If you are using Access 2007 or later you can rename the .accde to a .accdr to force Access into runtime mode.
Ever time my front end opens is chgeck to see id it is compiled (.mde/accd)e and is it is then runs the lock down code. Next is it checks to see if Access is in runtime mode. If not, it shuts down. After I compile a front end into a .accde/.mde I open it once to lock it down. It is now ready to deployment.
TIP: Backup! Test on copies or you can really get yourself locked out.
This may help:
10 tips for securing a Microsoft Access database - TechRepublic
