iptables - Regra recém-adicionada desaparece em poucos segundos Servidor Xenial

Question

Eu preciso adicionar uma regra para abrir a porta do Mosquitto:

$ sudo iptables -I INPUT 5 -p tcp --dport 1883 -j ACCEPT
$ sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:1883
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:2812
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:xmpp-client
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:5555
ACCEPT     tcp  --  anywhere             anywhere             tcp dpts:http-alt:8099
ACCEPT     tcp  --  anywhere             anywhere             tcp dpts:4380:4400
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:17443
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:17441
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:socks
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:1443
ACCEPT     all  --  appscale-image0      anywhere            
DROP       all  --  anywhere             anywhere            

Alguns segundos depois, a nova linha adicionada desaparece da seguinte forma:

$  sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  anywhere             anywhere            
ACCEPT     all  --  anywhere             anywhere             state RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:https
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:2812
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:xmpp-client
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:5555
ACCEPT     tcp  --  anywhere             anywhere             tcp dpts:http-alt:8099
ACCEPT     tcp  --  anywhere             anywhere             tcp dpts:4380:4400
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:17443
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:17441
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:socks
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:1443
ACCEPT     all  --  appscale-image0      anywhere            
DROP       all  --  anywhere             anywhere            

Alguma informação sobre esse misterioso desaparecimento? Não há trabalho cron executando. O ufw está desativado. Não sei como verificar qual serviço de firewall subjacente está sendo executado.