Scenario-based Nmap mastery: Moving from theory to practical exam application.
The CompTIA Security+ exam tests your ability to choose the least intrusive or most comprehensive command based on a set of constraints. Below are the most frequent scenarios you will encounter in the PBQ (Performance Based Questions) section.
Scenario A: The "Stealth Recon" Audit
"A security analyst needs to identify open ports on a server without completing a full TCP connection to avoid being logged by the application layer."
nmap -sS -T4 192.168.1.50
- Exam Logic: The
-sS(SYN Scan) is the key. It sends a SYN, waits for a SYN/ACK, but then sends a RST (Reset) instead of an ACK. This is known as "Half-Open" scanning.
Scenario B: Bypassing "No-Ping" Firewalls
"An administrator is trying to scan a host that is known to be 'Up', but the host is not responding to ICMP echo requests (Pings) because of a firewall."
nmap -Pn 10.0.0.25
- Exam Logic:
-Pntells Nmap to "Skip Host Discovery." It assumes the host is online and proceeds directly to port scanning.
Scenario C: Vulnerability & Version Discovery
"A technician needs to find out if an old web server is running an outdated version of Apache that is vulnerable to known exploits."
nmap -sV --script vuln 172.16.5.10
- Exam Logic:
-sV(Service Version) identifies the software version, and--script vulnuses the Nmap Scripting Engine (NSE) to check that version against a database of known vulnerabilities.
Quick-Fire Command Reference Table
| Requirement | Nmap Flag | Why it's used |
|---|---|---|
| Detect OS | -O |
Analyzes the TCP/IP stack to guess the Operating System. |
| Scan UDP Ports | -sU |
Finds DNS (53) or SNMP (161) services. |
| Export to XML | -oX filename.xml |
Essential for importing scan data into other tools like Nessus. |
| Full Aggressive | -A |
Combines -sV, -O, -sC, and traceroute. |
| Identify Top Ports | --top-ports 20 |
Scans only the 20 most common ports for maximum speed. |
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