View Full Version : [ubuntu] iptables firewalll to block all traffic except http

June 17th, 2008, 11:43 PM
iptables -P INPUT DROP
iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT

i would like to block everything , except http traffic, but is not working ???

June 18th, 2008, 01:48 AM
Can you please describe what exactly the machine is doing? Is it a sever or a client?

June 18th, 2008, 01:55 AM
it's a client, my desktop

June 18th, 2008, 03:11 AM
Ok. The reason why it is not working is you have all incoming UDP traffic blocked. UDP is used for DNS resolution (port 53). Also, since you are a client the http traffic inbound will have the source port 80 (rather than destination). Any outbound traffic is not affected. Try this:

sudo iptables -F
sudo iptables -P OUTPUT ACCEPT
sudo iptables -P FORWARD ACCEPT

sudo iptables -P INPUT DROP
sudo iptables -A INPUT -p udp -m udp --sport 53 -j ACCEPT
sudo iptables -A INPUT -p tcp -m tcp --sport 80 -j ACCEPT