How to block access to a local user to a local port?
Example: user Elvis should not have access to the port 25600 on the same server.
Iptables has an owner module that you can use
You would want to use
You just need to combine this with other suitable iptables parameters e.g. --dport to make the filter that works for you.
The full command as mentioned by Iain would look something like this
Just remember to edit the