PT0-002 Reconnaissance and Enumeration Practice Question
During a penetration test, you are asked to discover all live hosts on a subnet without generating excessive traffic or being too intrusive. Which Nmap command best achieves this goal?
⚠ Common exam trap
Test-takers frequently confuse `-sn` (ping scan) with `-sS` (SYN scan), assuming that a stealth scan is less intrusive, but `-sS` actually probes ports and generates more traffic, while `-sn` only checks for host liveness without port scanning.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
nmap -sn 192.168.1.0/24
The `-sn` flag (ping scan) sends ICMP echo requests, TCP SYN to port 443, TCP ACK to port 80, and ICMP timestamp requests to discover live hosts without performing port scans or service detection, minimizing traffic and intrusiveness. This meets the requirement of discovering all live hosts on a subnet efficiently.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
nmap -O 192.168.1.0/24
Why it's wrong here
-O performs OS detection but typically requires open ports, and it is more intrusive than a simple host discovery.
- ✓
nmap -sn 192.168.1.0/24
Why this is correct
-sn performs host discovery only (ping sweep) without port scanning, meeting the requirement.
- ✗
nmap -A 192.168.1.0/24
Why it's wrong here
Using `nmap -A` would generate excessive traffic and be highly intrusive, directly contravening the scenario's requirements. The `-A` flag activates aggressive scanning, encompassing OS detection, version detection, script scanning, and traceroute, all of which are resource-intensive operations that increase network noise. This option is tempting as `-A` provides comprehensive reconnaissance, making it ideal when detailed service and OS information is paramount and a higher level of intrusiveness is acceptable for a thorough assessment.
- ✗
nmap -sS 192.168.1.0/24
Why it's wrong here
-sS is a SYN scan that performs port scanning, which is more intrusive than a simple ping sweep.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PT0-003 practice question is part of Courseiva's free CompTIA 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 PT0-003 exam.