Plutonium

I'm trying to host a private B01 Zombies server for me and my friends. The server works fine but no matter what I've tried I can't stop randoms from joining the server.
The dedicated_sp.cfg doesn't seem to include a line for g_password "" and even when added manually seems to have no effect on randoms joining. I've tried searching for ways to password protect it or take it off the server listing but nothing seems to work.
I would just use private match instead but it won't allow more than 2 players (including the host) to join the lobby whereas a dedicated server is allowing for 4 players to join concurrently
Any suggestions or advice would be appreciated