nf_conntrack: table full, dropping packet The above in some cases I've seen is a sign of a DOS attack or can occur if users are using services like torrenting, proxy, VPNetc... Do not take it lightly as the above can knock a server offline if the table becomes full and I've also seen full crashes and kernel panics shortly after. ........

This is a very basic method and won't work in all cases but will reduce the chance of torrenting/abuse by your server users. iptables -A INPUT -p tcp --destination-port 6881:6999 -j REJECT iptables -A OUTPUT -p tcp --source-port 6881:6999 -j REJECT........