You could add ports 2082 and 2083 to the APF firewall block list. That would stop anyone entering cPanel whilst still allowing you to access WHM on ports 2086/2087.
I think you missed his point - BackRack wants to perform maintenance on the server. If you want to stop users from checking emails, using forums, etc. then you may as well block all IPs other than your own from accessing the server.
What kind of maintenance on a Linux server needs this? Just wondering.
BTW, chirpys firewall has an option to block all access to an IP on the server. So I guess you could block all access to the main shared IP if you have multiple IPs and use another for getting in.
I thought about blocking the ports but wondered if there was a feature in WHM to do it or maybe a shell command.
The maintenace I am doing is easyapache Curl SSL and others when needed. Curl with SSL just will not update, so I am guessing that by stopping the customers from accessing the WHM might help. The server was replaced and I have to do a lot of updates, but wanted to keep the server online at the same time.