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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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Table of Contents
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Challenge
Create a Bash Script
Add four iptables rules that modify Chain INPUT in your Bash script:
- Flush the current iptables rules.
- Create a rule that accepts already established connections and any related packets.
- Create a rule that accepts all SSH traffic.
- Change the policy of Chain INPUT to drop all incoming traffic.
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Challenge
Run the Bash Script
- After running your Bash script, run
sudo iptables -Lagain. - 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.)
- After running your Bash script, run
What's a lab?
Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.
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We will provide the credentials and environment necessary for you to practice right within your browser.
Guided walkthrough
Follow along with the author’s guided walkthrough and build something new in your provided environment!
Did you know?
On average, you retain 75% more of your learning if you get time for practice.