pcap-analyzer

name: pcap-analyzer description: >- Analyzes network captures (pcap/pcapng) for digital forensics and reverse engineering. Use when examining packet captures, extracting network artifacts, investigating incidents, analyzing malware C2 traffic, or reconstructing network activity from capture files.

Pcap Network Capture Analysis

Perform automated network traffic analysis on pcap/pcapng files using scapy. Extract streams, DNS, HTTP, credentials, and files. Detect anomalies like beaconing, port scanning, C2 patterns, and data exfiltration.

When to Use

• Analyzing packet captures from incident response or forensic investigations
• Extracting network artifacts (files, credentials, DNS queries) from pcaps
• Detecting C2 beaconing, port scanning, or data exfiltration patterns
• Reconstructing HTTP sessions and downloaded files from captures
• Mapping network endpoints and communication patterns
• Analyzing malware network behavior from sandbox captures
• CTF challenges involving network forensics
• Investigating cleartext credential exposure in network traffic

When NOT to Use

• Live traffic capture — use tcpdump, Wireshark, or tshark directly
• Need Wireshark GUI features — open the pcap in Wireshark
• Analyzing encrypted TLS content — need SSLKEYLOGFILE and tshark
• NetFlow/IPFIX data — use flow analysis tools (nfdump, SiLK)
• Wireless-specific analysis (802.11) — use Aircrack-ng suite
• IDS/IPS rule matching — use Suricata or Snort

Quick Reference

Prerequisites

• Python 3.8+ with pip
• scapy: pip install scapy
• tshark (optional, recommended): Install Wireshark (brew install wireshark / apt install tshark)

Main Wrapper Script

{baseDir}/scripts/pcap-analyze.sh [options] <capture_file>

Options:

• -o, --output <dir> — Output directory for results (default: current dir)
• -s, --script <name> — Analysis script to run (can be repeated)
• -a, --script-args <args> — Arguments for the last specified script
• --bpf <filter> — BPF filter to apply before analysis
• --timeout <seconds> — Analysis timeout
• -v, --verbose — Verbose output
• -h, --help — Show help

Built-in Analysis Scripts

analyze_all.py

Comprehensive first-pass analysis. Best for initial triage of unknown captures.

Output files:

• {name}_summary.txt — Capture overview: packet count, time range, duration, data rates
• {name}_protocols.json — Protocol distribution by layer
• {name}_endpoints.json — Top talkers by packet and byte count
• {name}_conversations.json — Top IP-pair conversations
• {name}_interesting.txt — Notable findings categorized as cleartext protocols, unusual ports, large transfers, suspicious DNS, tunneling indicators

extract_streams.py

Reassemble TCP and UDP streams. Pass --host <ip> or --port <port> to filter, --max-streams <n> to limit output.

Output: {name}_streams.json + {name}_stream_{n}.bin per stream

extract_dns.py

Extract all DNS queries and responses with full record detail.

Output:

• {name}_dns.json — Queries, responses, record types, TTLs
• {name}_domains.txt — Unique domains queried
• {name}_dns_timeline.json — Temporal query analysis

extract_http.py

Extract HTTP transactions from raw TCP payloads. Handles chunked transfer encoding.

Output: {name}_http.json + {name}_http_bodies/ directory

export_endpoints.py

Map all network endpoints with service identification. Includes MAC addresses, ports, protocols, subnets, and connection 5-tuples.

Output: {name}_endpoints.json

export_statistics.py

Detailed traffic statistics: protocol hierarchy, packet size distribution, timing analysis, TCP flag distribution, TTL distribution with OS fingerprint hints.

Output: {name}_statistics.json

find_anomalies.py

Detect suspicious patterns: C2 beaconing (low coefficient of variation in connection intervals), port scanning, data exfiltration, DNS tunneling (high-entropy long subdomain labels), unusual protocol usage, cleartext sensitive data, and TLS anomalies.

Output: {name}_anomalies.json

extract_credentials.py

Find cleartext credentials: HTTP Basic/Digest auth, form POST data, FTP USER/PASS, SMTP AUTH, Telnet logins, session cookies, API keys. Passwords are partially redacted in output.

Output: {name}_credentials.json

extract_files.py

Carve files from HTTP responses, FTP transfers, SMTP attachments, and magic-byte detection in TCP streams. Computes MD5 hashes. Supports PDF, ZIP, PNG, JPEG, PE, ELF, GIF, GZIP, and more.

Output: {name}_files.json + {name}_extracted/ directory

Common Workflows

Triage an Unknown Capture

mkdir -p ./analysis
{baseDir}/scripts/pcap-analyze.sh -s analyze_all.py -o ./analysis capture.pcap
cat ./analysis/capture_summary.txt
cat ./analysis/capture_interesting.txt

Investigate Suspected C2 Traffic

{baseDir}/scripts/pcap-analyze.sh -s find_anomalies.py -o ./c2 capture.pcap
{baseDir}/scripts/pcap-analyze.sh -s extract_dns.py -o ./c2 capture.pcap
cat ./c2/capture_anomalies.json | jq '.beaconing'
cat ./c2/capture_anomalies.json | jq '.data_exfiltration'

Extract Files from HTTP Traffic

{baseDir}/scripts/pcap-analyze.sh -s extract_http.py -s extract_files.py -o ./files capture.pcap
cat ./files/capture_files.json | jq '.[].filename'
ls ./files/capture_extracted/

Credential Exposure Audit

{baseDir}/scripts/pcap-analyze.sh -s extract_credentials.py -o ./creds capture.pcap
cat ./creds/capture_credentials.json | jq 'to_entries | map(select(.value | length > 0))'

Network Forensics (Full Workflow)

mkdir -p ./forensics
{baseDir}/scripts/pcap-analyze.sh \
    -s analyze_all.py \
    -s export_endpoints.py \
    -s extract_dns.py \
    -s find_anomalies.py \
    -s extract_credentials.py \
    -s extract_files.py \
    -o ./forensics evidence.pcap

Filter Analysis to Specific Host

{baseDir}/scripts/pcap-analyze.sh \
    --bpf "host 192.168.1.100" \
    -s analyze_all.py \
    -o ./host_analysis capture.pcap

{baseDir}/scripts/pcap-analyze.sh \
    -s extract_streams.py \
    -a "--host 192.168.1.100" \
    -o ./host_analysis capture.pcap

Troubleshooting

scapy Not Installed

pip install scapy

Large Capture Files

For captures over 100MB, use BPF filters to narrow scope:

{baseDir}/scripts/pcap-analyze.sh --bpf "tcp port 80" -s extract_http.py capture.pcap

Or use individual scripts instead of analyze_all.py.

Permission Errors Reading Pcap

chmod 644 capture.pcap
# Or run with sudo if needed

tshark Not Found

tshark is optional. All scripts work with scapy alone. For best results:

# macOS
brew install wireshark

# Debian/Ubuntu
sudo apt install tshark

# Fedora/RHEL
sudo dnf install wireshark-cli

Tips

1. Start with analyze_all.py — gives a full overview for triage
2. BPF filters reduce noise — use --bpf to focus on specific hosts or protocols
3. Use jq for JSON — all JSON exports are designed for machine processing
4. Combine with angr/Frida — extract a binary from pcap, then analyze with angr or trace with Frida
5. Large pcaps — filter first, analyze second; scapy loads entire capture into memory
6. Credentials are redacted — extract_credentials.py partially masks passwords for safe reporting