Port Blocking

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Revision as of 10:04, 5 January 2008 by Cyph3r (Talk | contribs)
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This tutorial will show you basic commands for blocking traffic from accessing your network.

Example:

Web = Port 80
FTP = Port 21

In order to set rules on specific ports, you need to access iptables. You will have greater control accessing the iptables via SSH or Telnet. If you feel more comfortable running commands via the router's web interface, then you can do so by logging into your router's Administration/Diagnostics page. From there you can input your desired commands into the Command Shell.

Commands

Port Blocking - Block all users to this port (Example: Port 80):

iptables -I FORWARD 1 -p tcp --dport 80 -j DROP

Port Blocking - Block a SINGLE user to this port (Example: Port 21):

iptables -I FORWARD 1 -s 192.168.1.101 -p tcp --dport 21 -j DROP

List iptables - List the rules in a chain or all chains:

iptables -L

Undo Rule - Delete rule rulenum (1 = first) from chain:

iptables -D FORWARD 1

Flush Rules from iptables - Delete all rules in chain or all chains:

iptables -F

Multiple Ports - Use a semi-colon to separate multiple ports, Use a different rulenum per command:

iptables -I FORWARD 1 -p tcp --dport 80 -j DROP; iptables -I FORWARD 2 -p tcp --dport 21 -j DROP

Port Range - Use a colon to select a port range (Port 21 through 80 will be closed):

iptables -I FORWARD 1 -p tcp --dport 21:80 -j DROP

External Resources

Iptables command - Lists all available commands for use in iptables
PortForward - List of the most commonly used ports
Telnet/SSH and the Command Line - How to on Telnet and SSH