Seria mais seguro se você mantivesse iptables e configurasse as regras corretas para abrir as portas do Minecraft. Eu procederia da seguinte forma:
nano /etc/iptables.rules
inserir
# 1. Delete all existing rules
iptables -F
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP
# 2. Accept established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# 3. Allow all outgoing traffic
-A OUTPUT -j ACCEPT
# 4. Allow Minecraft - default ports
-A INPUT -p tcp --dport 25565 -j ACCEPT
# 5. Reject everything else
-A INPUT -j REJECT
-A FORWARD -j REJECT
reinicie o firewall com novas regras
iptables-restore < /etc/iptables.rules
carrega cada vez que o servidor inicia
iptables-save > /etc/iptables.rules