dpkg -l | grep iptables 

On Ubuntu, iptables is not a service. In order to stop it, you have to do the following :

sudo iptables-save > /root/firewall.rules 

iptables -X 
iptables -t nat -F 
iptables -t nat -X 
iptables -t mangle -F 
iptables -t mangle -X 
iptables -P INPUT ACCEPT 
iptables -P FORWARD ACCEPT 
iptables -P OUTPUT ACCEPT 

In order to restore your previous rules :

iptables-restore < /root/firewall.rules 

to drop more rules：
iptables -t nat -P PREROUTING ACCEPT
iptables -t nat -P POSTROUTING ACCEPT
iptables -t nat -P OUTPUT ACCEPT
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -P PREROUTING ACCEPT
iptables -t mangle -P INPUT ACCEPT
iptables -t mangle -P FORWARD ACCEPT
iptables -t mangle -P OUTPUT ACCEPT
iptables -t mangle -P POSTROUTING ACCEPT
iptables -t mangle -F
iptables -t mangle -X
iptables -t filter -P INPUT ACCEPT
iptables -t filter -P FORWARD ACCEPT
iptables -t filter -P OUTPUT ACCEPT
iptables -t filter -F
iptables -t filter -X