iptables -N MMORPG

...

# match all mmorpg packets
iptables -A OUTPUT -p tcp --dport 1234 -j MMORPG
iptables -A OUTPUT -p tcp --dport 5678 -j MMORPG

...

iptables -A MMORPG -m condition --condition mmorpg_enabled -m limit --limit 1/minute -j LOG --log-prefix MMORPG_ACTIVE
iptables -A MMORPG -m condition --condition mmorpg_enabled -j ACCEPT
iptables -A MMORPG -j DROP