blocking external addresses to reach my network

Hello,


I have a service 12001 tcp/udp running on my server 192.168.1.100.

now external users connect and i have no problem.

The Problem is that i deleted some users. Now when i open my logs on server

i see that they still try to reach my service from external address. They cant

connect cause they do not have the correct user and pass ;)

But how do i block those external addresses for specific users to be blocked

at the firewall level.

Thanks a lot