Quick Answer
The answer is tcpdump, the essential command-line tool for full packet capture in network forensics. It is the correct choice because tcpdump captures raw traffic directly at the link layer, allowing it to collect every packet traversing a SPAN port without default filtering, which is critical for preserving a complete binary PCAP file for later analysis. On the Computer Hacking Forensic Investigator CHFI exam, this question tests your understanding of headless, low-overhead capture tools versus GUI-based alternatives like Wireshark, which require a display server and may drop packets under heavy load. A common trap is choosing a tool that only captures packet headers or performs protocol analysis in real time, whereas tcpdump’s raw capture ensures no data is lost during an ongoing compromise. For a memory tip, remember that tcpdump is the “dump truck” for network packets—it dumps everything onto the disk without sorting, leaving the analysis for later.
This CHFI practice question tests your understanding of network and cloud forensics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A forensic investigator needs to capture network traffic from a SPAN port on a switch to analyze an ongoing compromise. Which tool should the investigator use to collect the full packet capture (pcap) for later analysis?
NetFlow
Why wrong: NetFlow provides flow records, not full packet payloads.
nmap
Why wrong: nmap is a network scanner, not a packet capture tool.
Wireshark
Why wrong: Wireshark is primarily for analysis; tcpdump is preferred for headless capture.
tcpdump
tcpdump captures full packets and writes to pcap format.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
tcpdump
tcpdump is a command-line packet capture utility that captures raw network traffic at the link layer, making it ideal for collecting full packet captures (PCAP) from a SPAN port. Unlike GUI tools, it can run headless on a forensic workstation and write binary PCAP files for later analysis with tools like Wireshark. It captures all packets traversing the SPAN port without filtering by default, ensuring a complete record of the compromise.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
NetFlow
Why it's wrong here
NetFlow provides flow records, not full packet payloads.
nmap
Why it's wrong here
nmap is a network scanner, not a packet capture tool.
Wireshark
Why it's wrong here
Wireshark is primarily for analysis; tcpdump is preferred for headless capture.
tcpdump
Why this is correct
tcpdump captures full packets and writes to pcap format.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between flow-based monitoring (NetFlow) and full packet capture (tcpdump), leading candidates to mistakenly choose NetFlow because it is associated with network monitoring, even though it lacks the payload data required for forensic analysis.
Detailed technical explanation
tcpdump uses libpcap (or WinPcap/Npcap on Windows) to place the network interface into promiscuous mode, which is essential when connected to a SPAN port because the switch forwards all monitored traffic to that port. The -w flag writes packets directly to a PCAP file in pcapng or pcap format, preserving timestamps and frame metadata per RFC 791 and IEEE 802.3. In real-world forensic operations, tcpdump is often run with a ring buffer (-C and -W flags) to manage disk space during prolonged captures of a compromise.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CHFI exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Network and Cloud Forensics — This question tests Network and Cloud Forensics — Read the scenario before looking for a memorised answer..
The correct answer is: tcpdump — tcpdump is a command-line packet capture utility that captures raw network traffic at the link layer, making it ideal for collecting full packet captures (PCAP) from a SPAN port. Unlike GUI tools, it can run headless on a forensic workstation and write binary PCAP files for later analysis with tools like Wireshark. It captures all packets traversing the SPAN port without filtering by default, ensuring a complete record of the compromise.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This CHFI practice question is part of Courseiva's free EC-Council certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CHFI exam.
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