200-201 Network Intrusion Analysis Practice Question
An analyst reviewing network alerts notices a rule triggered for 'ET SCAN NMAP -sU scan' based on traffic to a Linux server. The packet capture shows multiple UDP packets to various ports, and for closed ports, the server responds with ICMP Destination Unreachable (Port Unreachable). Which type of scan is being performed, and how should the analyst classify this alert?
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
✓
UDP scan; true positive
UDP scans send UDP packets; closed ports respond with ICMP Port Unreachable. This matches the alert signature, indicating a true positive for a UDP scan.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
TCP SYN scan; true positive
Why it's wrong here
The traffic is UDP, not TCP SYN.
- ✓
UDP scan; true positive
Why this is correct
The UDP scan is correctly detected by the alert, so it is a true positive.
- ✗
UDP scan; false positive
Why it's wrong here
It is a UDP scan, but the alert correctly identifies scanning activity, so it is a true positive, not false.
- ✗
TCP connect scan; true negative
Why it's wrong here
This is a UDP scan, not TCP, and an alert triggered means it is not a true negative (no alert).
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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