Packet Analysis with tcpdump

Packet Analysis with tcpdump

Learn packet analysis with tcpdump, one of the most important command-line tools for network security, troubleshooting, and digital forensics. In cybersecurity, you often need to answer simple but critical questions: Which host sent the traffic? Which protocol was used? What data crossed the wire? This course teaches you how to capture packets, filter noisy traffic with Berkeley Packet Filters (BPF), inspect packet contents, and work with PCAP files so you can investigate network activity with confidence.

Why It Matters

Many security tools summarize or interpret network events for you, but tcpdump shows the raw traffic itself. That makes it a foundational tool for SOC analysts, incident responders, penetration testers, and system administrators. If you can read a packet capture directly, you are less dependent on dashboards and better able to validate suspicious behavior for yourself.

This course focuses on practical packet capture and investigation skills. You will start with the basics of identifying network interfaces and capturing traffic, then progress to precise filtering, payload inspection, and offline PCAP analysis. The final challenge puts those skills together in a realistic security investigation.

What You Will Learn

• Capture live network traffic with tcpdump on the correct network interface.
• Use Berkeley Packet Filters (BPF) to isolate traffic by host, subnet, protocol, and port.
• Inspect raw packet contents in hexadecimal and ASCII form to spot meaningful application data.
• Save packet captures to PCAP files and reopen them later for offline analysis.
• Investigate suspicious traffic patterns and extract evidence from a noisy capture.

Course Roadmap

• Network Interface and Basic Capture: Learn how to identify active interfaces, start a capture, and interpret the default tcpdump output.
• Berkeley Packet Filters (BPF): Reduce noise by filtering traffic with targeted expressions for IP addresses, subnets, ports, and protocols.
• Inspecting Packet Contents: View packet payloads in hex and ASCII so you can inspect unencrypted data and recognize suspicious content.
• PCAP File Management: Write captures to PCAP files, reopen them later, and analyze them efficiently in an offline workflow.
• Network Traffic Investigation: Apply everything in a challenge where you investigate a suspected breach and extract key forensic evidence.

Who This Course Is For

• Beginners who want a practical introduction to packet sniffing and network forensics.
• SOC analysts who need stronger command-line packet capture skills.
• Penetration testers who want to validate network behavior during assessments.
• Linux users who want to troubleshoot services and understand traffic at the packet level.

Outcomes

By the end of this course, you will be able to use tcpdump for command-line packet analysis, targeted traffic filtering, PCAP review, and basic network forensic investigation. You will also have the foundation needed for later courses that go deeper into protocol analysis and threat hunting.