Filter DNS Communications

Introduction

In this challenge, you will assume the role of a network security analyst at CyberDefend Inc. tasked with monitoring DNS traffic on your company's network due to suspicious activities suggesting potential DNS tunneling attacks. Your objective is to isolate and capture only DNS communications for further security analysis.

Using Wireshark, you'll need to apply the appropriate capture filter "udp port 53" to specifically target DNS traffic, capture at least 10 packets, and save them as a pcapng file in the designated directory. This practical exercise will help you develop essential skills in network traffic filtering and protocol analysis, which are crucial for identifying and investigating potential security threats in network communications.

Skills Graph

Filter DNS Communications

As a network security analyst at CyberDefend Inc., you've been tasked with monitoring DNS traffic on your company's network. Recent suspicious activities suggest potential DNS tunneling attacks. Your job is to isolate and capture only DNS traffic for further analysis.

Tasks

• Use Wireshark with the capture filter "udp port 53" to collect only DNS traffic and save the captured packets as dns_capture.pcapng in the /home/labex/project directory

Requirements

1. Launch Wireshark from the terminal or application menu.
2. Configure a capture filter using Berkeley Packet Filter (BPF) syntax to capture only DNS traffic. The correct filter expression is udp port 53.
3. Capture at least 10 packets of DNS traffic.
4. Save the captured packets in the file /home/labex/project/dns_capture.pcapng.
5. Do not modify the captured file after saving it.

Examples

When you've successfully completed the challenge, your Wireshark window should look similar to this:

• The packet list will show only DNS query and response packets
• The protocol column will show DNS for most packets
• The info column will show queries for domains like google.com, facebook.com, etc.
• The source and destination ports will include port 53

Hints

• DNS typically uses UDP on port 53, but can sometimes use TCP port 53 as well. For this challenge, focusing on UDP port 53 is sufficient.
• To set a capture filter in Wireshark, look for the "Capture Filter" field in the main interface or in the Capture Options dialog.
• Make sure to select an appropriate network interface where traffic is flowing (typically the primary network adapter or "any").
• Allow the capture to run for at least 30 seconds to ensure you collect enough DNS packets.
• You can stop the capture by clicking the red square button in the Wireshark toolbar.
• To save the capture, use File > Save As from the Wireshark menu.

Summary

In this challenge, I assumed the role of a network security analyst at CyberDefend Inc. tasked with monitoring DNS traffic for potential tunneling attacks. I learned how to use Wireshark to isolate DNS communications by configuring a capture filter with the Berkeley Packet Filter (BPF) syntax "udp port 53", which specifically targets DNS traffic.

The exercise required launching Wireshark, applying the appropriate capture filter, collecting at least 10 DNS packets generated from nslookup queries to domains like google.com and facebook.com, and saving the captured data to a specified location. This practical application demonstrated how security professionals can focus on specific protocol traffic when investigating network communications, allowing for more efficient analysis of potential security threats.