I have a question about which ports on my Centos 6.7 VPS I can safely close or move to harden the server a bit. I should say that there are only two users with only email accounts, so no FTP or anything like that.
Also, I have the following fail2ban jails activated:
These are the open ports:
The TCP /UDP DNS port. I don't believe this can be moved or closed?
TLS/SSL (HTTPS) I don't believe this can be moved?
UDP HTTP I don't believe this can be moved or closed?
POP3 Can I / should I move this by changing the port and then also changing the port on the users side? Will this break email?
SMTP Can I / should I move this by changing the port and then also changing the port on the users side? Will this break email?
SMTP I tried to close this in the past and I could no longer receive emails, so I'm leaving it as it is.
Any help appreciated.