[SOLVED] Closing open ports in Debian 10

andy657 · 02-17-2021, 08:31 PM

Hi all,

I recently setup an email server using iRedMail. Everything is working perfectly I'm just having issues closing open ports with nftables.

I'm currently trying to close port 110...

This is what I have done so far... I removed the rule in the /etc/nftables.conf file for port 110 and restarted the service - sudo systemctl restart nftables.service

Unfortunately when I scan the port with nmap it's still showing as being opened.

What additional steps do I have to do in order to close this port?

Thanks for the help...

Pentium4User · 02-18-2021, 12:11 AM

An open port results in a software listening on this port.
If no software listens on this port, it is closed and on TCP ports it will send TCP-RESET.
This is the right way to get rid off it.
Check with

Code:

fuser 110/tcp

which PID the process has and then check what application it is.

110 TCP is the well-known port for POP3, so maybe you need to disable POP3 in you mail server.
This is the right way instead of using a firewall to block it.