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I want to make some simple iptables rules to deny all incoming connections and allow outgoing. How can I do that?

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up vote 8 down vote accepted

Try this with root access :

# Set default chain policies
iptables -P INPUT DROP
iptables -P FORWARD DROP

# Accept on localhost
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

# Allow established sessions to receive traffic
iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
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When I do first line of your rule, i've got disconnected from SSH – holms Oct 6 '14 at 7:26
The question is "deny all incoming connections" and not "deny all incoming connections except SSH" :) – Yohann Dec 4 '14 at 16:17

If you’re working remotely via SSH, you might want to add this (-I inserts it before all other rules in INPUT):

iptables -I INPUT -p tcp --dport 22 -j ACCEPT

If your SSH service is listening on another port, you’ll have to use that port instead of 22.

Otherwise, you might accidentally lose access.

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