If someone is relatively experienced with Access the only sure way to prevent it is in how you develop your database and lock it down by making it a ACCDE file.

Access Security Seminar

Also:  Simple Security

I use the UserID field as an index that is searchable for everything else.  I do want users to see the id field, but I don't want them to overwrite it when they are in a record.

Open up the properties for that field and set Locked to True.

Or just make it an Autonumber. Can't change those. :)