Cybersecurity Triage

Show iptables INPUT Rules

You need a concise view of the iptables INPUT chain policy and rules.

Command

iptables -S INPUT

What changed

Nothing changes. iptables prints the INPUT chain in a reusable rule format.

Danger

safe

When to use it

Use on systems where iptables rules may still be active or where tooling reports iptables syntax.

When not to use it

Do not assume iptables output covers nftables-native rules on every modern distribution.

Undo or recovery

No undo needed because this command is read-only.

Expected output

INPUT policy and append rules for accepted or dropped traffic.

demo script

Disposable terminal steps

iptables -S INPUT
iptables -S INPUT | grep -- '--dport'

Terminal transcript Demo JSON

simulated output

What it looks like

disposable vessel

::fixture-ready::
$ iptables -S INPUT
-P INPUT DROP
-A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -s 203.0.113.0/24 --dport 22 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 80,443 -j ACCEPT
-A INPUT -p tcp --dport 25 -j ACCEPT
-A INPUT -p tcp --dport 5432 -j DROP
::exit-code::0
$ iptables -S INPUT | grep -- '--dport'
-A INPUT -p tcp -s 203.0.113.0/24 --dport 22 -j ACCEPT
-A INPUT -p tcp -m multiport --dports 80,443 -j ACCEPT
-A INPUT -p tcp --dport 25 -j ACCEPT
-A INPUT -p tcp --dport 5432 -j DROP
::exit-code::0

YouTube Short

Read iptables INPUT rules.

On older or mixed systems, iptables output can explain why traffic is allowed or dropped.

experiments

A/B tests to run

Metric: save_rate

A: Legacy rules still matter.

B: Print INPUT rules safely.