Iptables provide filtering, NAT and other packet mangling.
Viewing current configuration
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iptables -L |
Output will be like
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Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination |
Storing iptables rules in a file
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nano -w /etc/iptables.test.rules |
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*filter # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0 -A INPUT -i lo -j ACCEPT -A INPUT -i ! lo -d 127.0.0.0/8 -j REJECT # Accepts all established inbound connections -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # Allows all outbound traffic # You could modify this to only allow certain traffic -A OUTPUT -j ACCEPT # Allows HTTP and HTTPS connections from anywhere (the normal ports for websites) -A INPUT -p tcp --dport 80 -j ACCEPT -A INPUT -p tcp --dport 443 -j ACCEPT # Allows SSH connections for script kiddies # THE -dport NUMBER IS THE SAME ONE YOU SET UP IN THE SSHD_CONFIG FILE -A INPUT -p tcp -m state --state NEW --dport 30000 -j ACCEPT # Now you should read up on iptables rules and consider whether ssh access # for everyone is really desired. Most likely you will only allow access from certain IPs. # Allow ping -A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT # log iptables denied calls (access via 'dmesg' command) -A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7 # Reject all other inbound - default deny unless explicitly allowed policy: -A INPUT -j REJECT -A FORWARD -j REJECT COMMIT |
Activate these new rules:
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iptables-restore < /etc/iptables.test.rules |
See the difference
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iptables -L |
If you are happy then save new rules to master iptables file
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iptables-save > /etc/iptables.up.rules |
To make sure the iptables rules are started on a reboot we’ll create a new file
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nano -w /etc/network/if-pre-up.d/iptables |
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#!/bin/bash /sbin/iptables-restore < /etc/iptables.up.rules |
Set permission
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chmod +x /etc/network/if-pre-up.d/iptables |
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[…] InfinitelyGalactic how to setup and configure iptables firewall on debian. Continued here: Handling iptables on Debian OS – MyLiteratureTechLife.COM This entry was posted in Uncategorized and tagged firewall-on-debian by InfinitelyGalactic. […]