Packet Analysis
Packet analysis is the process of capturing and inspecting network traffic to understand the data being transmitted. It is essential for troubleshooting, security monitoring, and performance optimization.
Table of Contents
- 1. Introduction
- 2. Capturing Packets
- 3. Analyzing with Wireshark
- 4. Common Protocols
- 5. Best Practices
- 6. References
1. Introduction
Network packets are the basic units of data transmission. Analyzing them reveals the structure, payload, and any anomalies that may indicate misconfigurations or malicious activity.
2. Capturing Packets
Tools such as tcpdump and Wireshark allow you to intercept traffic on an interface. Below is a common tcpdump command:
sudo tcpdump -i eth0 -w capture.pcap -c 5000This captures 5,000 packets on eth0 and writes them to capture.pcap.
3. Analyzing with Wireshark
Wireshark provides a graphical interface to dissect each packet. Key features include:
- Protocol decoding
- Color rules for quick identification
- Follow TCP/UDP streams
Example: Follow a TCP stream to view the full conversation.
Right‑click → Follow → TCP Stream4. Common Protocols
| Protocol | Port(s) | Typical Use |
|---|---|---|
| HTTP | 80 | Web traffic |
| HTTPS | 443 | Secure web traffic |
| DNS | 53 | Domain name resolution |
5. Best Practices
- Capture only what you need – use filters to limit traffic.
- Sanitize sensitive data before sharing captures.
- Keep capture files organized with timestamps.
- Document the capture environment (interface, filters, system state).