Top 10 HDSniff Commands Every Analyst Should KnowHDSniff is a lightweight packet-capture and analysis tool often used by network analysts and security professionals for quick diagnostics, forensic collection, and protocol inspection. This article covers the top 10 HDSniff commands every analyst should know, why they matter, and practical examples showing how to use them effectively in real-world situations.
1. Basic capture: hd sniff -i -w
What it does: Captures raw packets from a network interface and writes them to a file.
Why it matters: Most analysis workflows start with capturing traffic for later inspection or evidence preservation. This command creates a pcap file compatible with tools like Wireshark or tcpdump.
Example:
hdsniff -i eth0 -w capture1.pcap Tips:
- Run with elevated privileges (sudo) if required.
- Use a capture file name that includes date/time for traceability.
2. Capture with filter: hdsniff -i -w -f “”
What it does: Applies a Berkeley Packet Filter (BPF) to capture only matching packets.
Why it matters: Reduces storage and noise by saving only relevant traffic (e.g., specific hosts, ports, or protocols).
Example:
hdsniff -i eth0 -w web_traffic.pcap -f "tcp port 80 or tcp port 443" Common filters:
- host 10.0.0.5
- net 192.168.1.0/24
- port 53
3. Read pcap file: hdsniff -r
What it does: Reads and displays packet contents from a saved pcap file.
Why it matters: Useful for quick command-line review without opening a GUI.
Example:
hdsniff -r capture1.pcap Tip: Combine with text-processing tools (grep, awk) to extract specific lines.
4. Show summary/statistics: hdsniff -s or -S during capture
What it does: Displays high-level statistics such as packet counts, protocol distribution, and capture duration.
Why it matters: Quick way to understand traffic composition and spot anomalies or spikes.
Example:
hdsniff -s capture1.pcap If using live capture, use the runtime stats flag:
hdsniff -i eth0 -S 5. Follow TCP stream: hdsniff –follow-tcp -r
What it does: Reconstructs and displays the full TCP stream for a chosen packet or connection.
Why it matters: Essential for analyzing sessions, extracting HTTP requests/responses, or reconstructing file transfers.
Example:
hdsniff --follow-tcp 152 -r capture1.pcap Note: Packet number is obtained from a prior listing or summary.
6. Protocol decode: hdsniff –decode -r
What it does: Forces decoding of packets using a specific protocol dissector (for example, HTTP, DNS, TLS).
Why it matters: Helps when HDSniff doesn’t auto-detect or when you want deeper parsing of a protocol’s fields.
Example:
hdsniff --decode http -r web_traffic.pcap Common decoders: http, dns, tls, smtp, ftp.
7. Extract files/payloads: hdsniff –extract -r -o
What it does: Extracts embedded files or payload data (attachments, downloads, images) from captured sessions.
Why it matters: Speeds up forensic tasks by saving recovered files for separate inspection or malware analysis.
Example:
hdsniff --extract -r capture1.pcap -o ./extracted_files Caveat: Verify extracted files in a safe analysis environment (sandbox).
8. Export flows: hdsniff –export-flows -r -o flows.csv
What it does: Aggregates packets into flows and exports metadata (source/dest IPs, ports, byte/packet counts, start/end times) to CSV.
Why it matters: Useful for timeline analysis, anomaly detection, or feeding other tools (SIEMs, spreadsheets).
Example:
hdsniff --export-flows -r capture1.pcap -o flows.csv You can then open flows.csv in Excel or import into a database for queries.
9. Live capture with rotation: hdsniff -i -w capture-%Y%m%d%H%M%S.pcap -C -W
What it does: Captures live traffic with file rotation by size or time, keeping a fixed number of files.
Why it matters: Prevents disk exhaustion during long captures and keeps recent history.
Example:
hdsniff -i eth0 -w capture-%Y%m%d%H%M%S.pcap -C 500 -W 10 This rotates files at 500 MB and keeps the 10 most recent files.
10. Verbose/troubleshooting mode: hdsniff -v or -vv
What it does: Provides verbose logging and diagnostic messages about packet parsing, errors, and internal decisions.
Why it matters: Helpful when diagnosing why packets aren’t decoded as expected or when debugging capture issues.
Example:
hdsniff -i eth0 -w debug_capture.pcap -vv Use sparingly—verbose logs can be large.
Practical workflow example
- Start rotated capture with filtering for web traffic:
hdsniff -i eth0 -w web-%Y%m%d%H%M%S.pcap -f "tcp port 80 or tcp port 443" -C 200 -W 12 - After an incident, export flows and get a summary:
hdsniff -s web-20250831...pcap hdsniff --export-flows -r web-20250831...pcap -o incident_flows.csv - Follow suspicious TCP stream(s) and extract files:
hdsniff --follow-tcp 87 -r web-20250831...pcap hdsniff --extract -r web-20250831...pcap -o ./incident_files
Best practices and safety
- Capture only what you need with BPF filters to reduce data volume and privacy exposure.
- Keep captures on secure storage and follow your organization’s retention policies.
- Analyze extracted executables in an isolated sandbox.
- Use timestamps and consistent naming for chain-of-custody clarity.
Conclusion
Mastering these top 10 HDSniff commands lets analysts capture efficiently, reduce noise, reconstruct sessions, and extract artifacts for forensic analysis. Familiarity with BPF filters, flow exports, and stream reconstruction will speed investigations and improve accuracy.
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