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How to check whether any netfilter rules are set on a host

+1 vote
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Is there a way to find out if there any iptables rules set on a machine ?

There are some indirect ways which will not always work; for example, I know that on most hosts, iptables -S will return the following output (when no iptable rules are set)
-P INPUT ACCEPT
-P FORWARD ACCEPT
-P OUTPUT ACCEPT

So you can check whether or not the number of output lines is greater than 3 (as an indication of whether or not iptables rules are set). But there are hosts on which there are more chains then these 3; these chains are set by application/services, even without any iptable rules which are set. And after running iptables -F on these machines, iptables -S will still show more than 3 chains, even that there are no iptables rules set in these chains.

So the question is - is there a way to know whether or not netfilter rules are set on a host, regardless of the number of chains ?

posted Nov 29, 2016 by anonymous

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