Firewall basics (ufw, iptables) in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable the UFW firewall.

Linux CLI

sudo ufw [1]

Drag options to blanks, or click blank then click option'

Adisable

Benable

Cstatus

Dreset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'disable' instead of 'enable' will turn the firewall off.

Using 'status' only shows the current state, it does not enable the firewall.

Use ufw enable to turn on the firewall.

2fill in blank

medium

Complete the code to allow incoming SSH connections using UFW.

Linux CLI

sudo ufw [1] ssh

Drag options to blanks, or click blank then click option'

Areject

Bdeny

Callow

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'deny' or 'reject' blocks SSH connections.

Using 'limit' restricts connections but does not fully allow them.

Use ufw allow ssh to permit SSH traffic through the firewall.

3fill in blank

hard

Fix the error in the iptables command to list all rules with line numbers.

Linux CLI

sudo iptables -[1] --line-numbers

Drag options to blanks, or click blank then click option'

AL

Blist

CS

DN

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase 'l' causes an error.

Using 'list' as a full word is not valid in iptables options.

The correct option to list rules is -L. It shows all rules with optional line numbers.

4fill in blank

hard

Fill both blanks to add a rule that drops incoming TCP packets on port 80 using iptables.

Linux CLI

sudo iptables -A INPUT -p [1] --dport [2] -j DROP

Drag options to blanks, or click blank then click option'

Atcp

Budp

C80

D22

Attempts:

3 left

💡 Hint

Common Mistakes

Using UDP instead of TCP will not match HTTP traffic.

Using port 22 blocks SSH, not HTTP.

Use protocol tcp and port 80 to drop HTTP traffic.

5fill in blank

hard

Fill all three blanks to create a UFW rule that limits incoming connections on port 22.

Linux CLI

sudo ufw [1] [2]/[3]

Drag options to blanks, or click blank then click option'

Alimit

B22

Ctcp

Ddeny

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'deny' blocks all connections instead of limiting.

Omitting the protocol may cause the rule to be less specific.

The command ufw limit 22/tcp limits SSH connections to prevent brute force attacks.