Duki 552 Nearly a Posting Virtuoso

Hey everyone. I'm the network admin for a ~20 user network, but I am not very experienced in a lot of ways. Myself and another tech recently changed the domain name from .com to .local due to DNS problems. I've noticed that the SYSVOL and NETLOGON folders are showing up when users browse the network. What are the potential threats of users being able to access these folders, and how can I hide them without disrupting access to the DC (pertaining to logging on mainly)?

I've tried a couple things before, but inadvertently I block users from logging on. :-| heheh