Use Scapy to craft, send, sniff, and dissect TCP/UDP/ICMP/DNS packets, analyze pcap files, implement SYN scans, and detect anomalous traffic such as fragmented or malformed packets. Use when performing authorized network reconnaissance, protocol-level forensic analysis, or building traffic anomaly detection during security testing.
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Use analyzing-network-packets-with-scapy to analyze [pcap or pcapng file] and produce a structured report of protocol statistics and suspicious traffic indicators.
Required inputs
[pcap or pcapng file]
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SKILL.md
name: analyzing-network-packets-with-scapydescription: Use Scapy to craft, send, sniff, and dissect TCP/UDP/ICMP/DNS packets, analyze pcap files, implement SYN scans, and detect anomalous traffic such as fragmented or malformed packets. Use when performing authorized network reconnaissance, protocol-level forensic analysis, or building traffic anomaly detection during security testing.domain: cybersecuritysubdomain: network-securitytags: - scapy- packet-analysis- network-forensics- protocol-dissection- pcap- traffic-analysisversion: '1.0'author: mahipallicense: Apache-2.0nist_csf: - PR.IR-01- DE.CM-01- ID.AM-03- PR.DS-02mitre_attack: - T1040- T1071- T1046- T1557
Analyzing Network Packets with Scapy
Overview
Scapy is a Python packet manipulation library that enables crafting, sending, sniffing, and dissecting network packets at granular protocol layers. This skill covers using Scapy for security-relevant tasks including TCP/UDP/ICMP packet crafting, pcap file analysis, protocol field extraction, SYN scan implementation, DNS query analysis, and detecting anomalous traffic patterns such as unusually fragmented packets or malformed headers.
When to Use
When investigating security incidents that require analyzing network packets with scapy
When building detection rules or threat hunting queries for this domain
When SOC analysts need structured procedures for this analysis type
When validating security monitoring coverage for related attack techniques
Prerequisites
Python 3.8+ with scapy library installed (pip install scapy)
Root/administrator privileges for raw socket operations (sniffing, sending)
Npcap (Windows) or libpcap (Linux) for packet capture
Authorization to perform packet operations on target network
Steps
Read and parse pcap/pcapng files with rdpcap() for offline analysis
Extract protocol layers (IP, TCP, UDP, DNS, HTTP) and field values
Compute traffic statistics: top talkers, protocol distribution, port frequency
Detect SYN flood patterns by analyzing TCP flag ratios
Identify DNS exfiltration indicators via query length and entropy analysis
Craft custom probe packets for authorized network testing
Export findings as structured JSON report
Expected Output
JSON report containing packet statistics, protocol distribution, top source/destination IPs, detected anomalies (SYN floods, DNS tunneling indicators, fragmentation attacks), and per-flow summaries.