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Blocking and Allowing Traffic with a Firewall

For the Security Exam, it is important to understand how firewall rules work. In this hands-on lab, we will configure a couple of firewall rules on iptables, which is built into CentOS. After completing this lab, you will understand how firewall rules work in a hierarchical manner to allow and block traffic.

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Path Info

Clock icon Beginner
Clock icon 1h 0m
Clock icon Nov 14, 2018

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Table of Contents

  1. Challenge

    Create a Bash Script

    Add four iptables rules that modify Chain INPUT in your Bash script:

    1. Flush the current iptables rules.
    2. Create a rule that accepts already established connections and any related packets.
    3. Create a rule that accepts all SSH traffic.
    4. Change the policy of Chain INPUT to drop all incoming traffic.
  2. Challenge

    Run the Bash Script

    1. After running your Bash script, run sudo iptables -L again.
    2. Compare and contrast the default rules to those you put into place with your Bash script. (You should get a feel for how the policy works to block any traffic not specifically allowed as well as how firewall rules look.)

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