hardMultiple ChoiceObjective-mapped
200-201 Practice Question: A security analyst detects a large number of TCP…
A security analyst detects a large number of TCP RST packets from a single external IP to various internal hosts. The internal hosts are not sending any corresponding packets. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the distinction between a TCP reset attack and a port scan, where candidates mistakenly associate RST packets with port scanning (e.g., receiving RST from a closed port) rather than recognizing unsolicited RST packets as an active attack.
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
✓
A TCP reset attack is being performed
A TCP reset attack (also known as a forged RST attack) occurs when an attacker sends spoofed TCP RST packets to disrupt an existing connection. The key clue is that the internal hosts are not sending any corresponding packets, indicating the RST packets are unsolicited and likely forged, which is characteristic of this attack rather than a normal network event.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A denial-of-service attack is occurring
Why it's wrong here
DoS typically floods with traffic, not specifically RST.
- ✗
A TCP connection is being established
Why it's wrong here
TCP establishment uses SYN, not RST.
- ✗
A port scan is in progress
Why it's wrong here
Port scans use SYN or other probes.
- ✓
A TCP reset attack is being performed
Why this is correct
Forged RST packets terminate connections prematurely.
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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.