200-201 Security Monitoring Practice Question
A security analyst is investigating a potential port scan. Which THREE patterns in NetFlow data would indicate a horizontal port scan?
⚠ Common exam trap
Cisco often tests the distinction between horizontal and vertical scans: the trap is confusing 'same destination port, multiple destination IPs' (horizontal) with 'multiple destination ports, same destination IP' (vertical).
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
✓
Low number of packets per flow
A horizontal port scan targets the same port across multiple destination IPs. In NetFlow, each connection attempt typically involves a low number of packets (often just a SYN) because the scanner does not complete the TCP handshake. This pattern of low packet counts per flow is a strong indicator of scanning activity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Low number of packets per flow
Why this is correct
Port scanners often send single SYN packets per connection attempt, resulting in low packet counts.
- ✓
Flows with SYN flag set but no subsequent SYN-ACK or RST
Why this is correct
This indicates incomplete handshakes typical of scans.
- ✗
Multiple connection attempts from the same source IP to the same destination IP on different ports
Why it's wrong here
Again, vertical scan.
- ✗
Single source IP, multiple destination ports on one destination IP
Why it's wrong here
This describes a vertical port scan, not horizontal.
- ✓
Single source IP, same destination port, multiple destination IPs
Why this is correct
This is the classic horizontal scan pattern.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.