I've got a server (CentOS 6.7) running, which causes me some headaches.
A few months ago, the website running on the server was unavailable. After some digging, it appeared that Iptables was blocking the server's own outgoing traffic. This happened by a rule automatically added by (I think) fail2ban.
Today, I got a similar problem; now the server was blocking outgoing traffic to two specific IP's, which are, unfortunately, important for the applications running on the server.
I've removed the rules, so now it's all working again, but how do I prevent this from happening again? How do I prevent fail2ban (and maybe friends) from adding rules which block outgoing traffic?