Wireshark packet capture basics in Cybersecurity - Mini Project: Build & Apply

Wireshark Packet Capture Basics

📖 Scenario: You are a network technician learning to use Wireshark to capture and analyze network packets. This helps you understand what data is moving through your network and troubleshoot issues.

🎯 Goal: Build a simple step-by-step guide to capture network packets using Wireshark, set a capture filter, start the capture, and stop it properly.

📋 What You'll Learn

Create a variable to hold the network interface name

Add a capture filter string to limit captured packets

Write the command to start the packet capture with the filter

Write the command to stop the packet capture

💡 Why This Matters

🌍 Real World

Network technicians and cybersecurity professionals use Wireshark to monitor and troubleshoot network traffic by capturing packets.

💼 Career

Knowing how to capture and filter packets is essential for diagnosing network problems and investigating security incidents.

1

Set the Network Interface

Create a variable called interface and set it to the string "eth0", which represents the network interface to capture packets from.

Cybersecurity

# Create a variable called interface and set it to "eth0"
# Your code here

Hint

The network interface is usually named like "eth0", "wlan0", or similar. Use exactly "eth0" here.

2

Add a Capture Filter

Create a variable called capture_filter and set it to the string "tcp port 80" to capture only HTTP traffic on port 80.

Cybersecurity

interface = "eth0"
# Create a variable called capture_filter and set it to "tcp port 80"
# Your code here

Hint

The capture filter limits packets to those using TCP on port 80, which is common for web traffic.

3

Start Packet Capture

Write a command string called start_capture_cmd that uses tshark to start capturing packets on the interface stored in interface with the filter stored in capture_filter. Use the format: "tshark -i {interface} -f '{capture_filter}'".

Cybersecurity

interface = "eth0"
capture_filter = "tcp port 80"
# Create start_capture_cmd using f-string with tshark command
# Your code here

Hint

Use an f-string to insert the variables into the command string exactly as shown.

4

Stop Packet Capture

Create a variable called stop_capture_cmd and set it to the string "pkill tshark" which stops the running tshark capture process.

Cybersecurity

interface = "eth0"
capture_filter = "tcp port 80"
start_capture_cmd = f"tshark -i {interface} -f '{capture_filter}'"
# Create stop_capture_cmd and set it to "pkill tshark"
# Your code here

Hint

The command pkill tshark stops the tshark process safely.

Practice

1. What is the primary purpose of Wireshark in cybersecurity?

easy

A. To capture and analyze network packets in real time

B. To encrypt network traffic for security

C. To block unauthorized network access

D. To create virtual private networks (VPNs)

Solution

1. Step 1: Understand Wireshark's function

   Wireshark is a tool designed to capture and display network packets as they travel through a network.

2. Step 2: Identify the correct purpose

   Among the options, only capturing and analyzing packets matches Wireshark's main use.

3. Final Answer:

   To capture and analyze network packets in real time -> Option A

4. Quick Check:

   Wireshark captures packets = To capture and analyze network packets in real time [OK]

Hint: Wireshark shows network data live, not encrypt or block [OK]

Common Mistakes:

• Confusing Wireshark with firewall or VPN tools
• Thinking Wireshark encrypts data
• Assuming Wireshark blocks traffic

2. Which of the following is the correct way to start a packet capture in Wireshark?

easy

A. Click on 'File' then 'Open Capture'

B. Click on 'Capture' then 'Start'

C. Click on 'Analyze' then 'Filter'

D. Click on 'Edit' then 'Preferences'

Solution

1. Step 1: Identify the menu for starting capture

   In Wireshark, the 'Capture' menu contains options to start or stop capturing packets.

2. Step 2: Match the correct action

   Clicking 'Capture' then 'Start' begins the live packet capture process.

3. Final Answer:

   Click on 'Capture' then 'Start' -> Option B

4. Quick Check:

   Start capture via Capture menu = Click on 'Capture' then 'Start' [OK]

Hint: Start capture under 'Capture' menu, not 'File' or 'Edit' [OK]

Common Mistakes:

• Choosing 'File' to start capture instead of 'Capture'
• Confusing 'Analyze' with starting capture
• Looking in 'Edit' menu for capture options

3. Consider the following Wireshark filter: ip.src == 192.168.1.10. What does this filter do?

medium

A. Shows packets where the destination IP is 192.168.1.10

B. Shows packets with any IP address except 192.168.1.10

C. Shows packets where the source IP is 192.168.1.10

D. Shows packets where either source or destination IP is 192.168.1.10

Solution

1. Step 1: Understand the filter syntax

   The filter ip.src == 192.168.1.10 means packets where the source IP address equals 192.168.1.10.

2. Step 2: Match filter meaning to options

   Only Shows packets where the source IP is 192.168.1.10 correctly describes packets with source IP 192.168.1.10.

3. Final Answer:

   Shows packets where the source IP is 192.168.1.10 -> Option C

4. Quick Check:

   ip.src filter = source IP = Shows packets where the source IP is 192.168.1.10 [OK]

Hint: ip.src means source IP, ip.dst means destination IP [OK]

Common Mistakes:

• Confusing source IP with destination IP
• Assuming filter matches both source and destination
• Thinking filter excludes the IP address

4. You tried to filter packets with tcp.port == 80 but no packets appear. What could be a likely reason?

medium

A. Port 80 is not used for TCP traffic

B. The filter syntax is incorrect

C. Wireshark does not support filtering by port

D. You captured packets on the wrong network interface

Solution

1. Step 1: Check filter syntax correctness

   The filter tcp.port == 80 is valid syntax to filter TCP packets on port 80.

2. Step 2: Consider capture context

   If no packets appear, a common cause is capturing on the wrong network interface where no HTTP traffic (port 80) passes.

3. Final Answer:

   You captured packets on the wrong network interface -> Option D

4. Quick Check:

   Wrong interface capture = no matching packets = You captured packets on the wrong network interface [OK]

Hint: No packets? Check if capturing on correct network interface [OK]

Common Mistakes:

• Assuming filter syntax is wrong without checking
• Believing Wireshark can't filter by port
• Thinking port 80 is not TCP by default

5. You want to capture only HTTP traffic from a specific device with IP 10.0.0.5 using Wireshark. Which filter should you apply?

hard

A. ip.addr == 10.0.0.5 and tcp.port == 80

B. ip.src == 10.0.0.5 or ip.dst == 10.0.0.5 and tcp.port == 80

C. ip.addr == 10.0.0.5 or tcp.port == 80

D. ip.src == 10.0.0.5 and tcp.port == 80

Solution

1. Step 1: Define the filter requirements

   You want packets where the device IP is either source or destination and the traffic is HTTP (TCP port 80).

2. Step 2: Analyze each filter option

   ip.addr == 10.0.0.5 and tcp.port == 80 uses ip.addr == 10.0.0.5 which matches source or destination IP, combined with tcp.port == 80 to filter HTTP traffic. This matches the requirement exactly.

3. Step 3: Identify issues in other options

   ip.src == 10.0.0.5 or ip.dst == 10.0.0.5 and tcp.port == 80 lacks parentheses, so 'or' and 'and' precedence causes incorrect filtering. ip.addr == 10.0.0.5 or tcp.port == 80 matches any packet with IP 10.0.0.5 or any TCP port 80 packet, which is too broad. ip.src == 10.0.0.5 and tcp.port == 80 only matches packets where 10.0.0.5 is source, missing destination packets.

4. Final Answer:

   ip.addr == 10.0.0.5 and tcp.port == 80 -> Option A

5. Quick Check:

   ip.addr covers both ends + tcp.port 80 = ip.addr == 10.0.0.5 and tcp.port == 80 [OK]

Hint: Use ip.addr for both source/destination IPs in filters [OK]

Common Mistakes:

• Not using parentheses causing wrong logic in filters
• Using only ip.src or ip.dst missing half the traffic
• Using 'or' instead of 'and' causing too many packets