That is kinda obvious and straightforward. Records that are saved electronically can be (and usually are) protected by passwords. I don’t think you need a reminder here of how a good password is created. Also, some PC systems only allow access by authorized person sign in with their unique password. Nowadays some computers are not even connected to the Internet to avoid the risk of intervention.
If the information is stored manually, not electronically, it can simply be locked away when not in use. There are plenty of possibilities to do that.