The answer is sending multiple connection requests to various ports on a single host, often without completing the full TCP handshake. This is characteristic of a port scan attack because the attacker sends SYN packets to probe for open ports; if a SYN-ACK is returned, the port is open, while an RST indicates a closed port. By never sending the final ACK to complete the three-way handshake, the attacker avoids establishing a full connection, which helps evade basic logging and intrusion detection systems. On the Cisco CyberOps Associate 200-201 exam, this concept tests your understanding of reconnaissance techniques and how attackers map network services stealthily. A common trap is confusing a full connection scan with a half-open SYN scan—remember that a true port scan attack typically leaves connections incomplete to stay under the radar. Memory tip: think “SYN, no ACK” for a stealthy port scan.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which TWO actions are characteristic of a port scan performed by an attacker? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Using TCP SYN packets without completing the three-way handshake.
A is correct because a TCP SYN scan sends a SYN packet to initiate a connection but never completes the three-way handshake by sending the final ACK. This allows the attacker to determine if a port is open (SYN-ACK received) or closed (RST received) without establishing a full connection, which helps evade some logging mechanisms.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Using TCP SYN packets without completing the three-way handshake.
Why this is correct
SYN scans are a common stealth scanning technique.
Related concept
Read the scenario before looking for a memorised answer.
✓
Sending multiple connection requests to various ports on a single host.
Why this is correct
This is a basic characteristic of a port scan.
Related concept
Read the scenario before looking for a memorised answer.
✗
Randomly selecting target ports without any pattern.
Why it's wrong here
Most scanners use sequential or known port lists.
✗
Spoofing the source IP address to evade detection.
Why it's wrong here
Spoofing is uncommon in port scans because the attacker needs responses; SYN scans use a real IP.
✗
Sending packets at a very low rate to avoid triggering threshold-based alerts.
Why it's wrong here
Low rate scanning is an evasion technique, not a defining characteristic of a port scan.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a port scan's core mechanism (SYN packets without completing the handshake) and optional evasion techniques (like low rate or IP spoofing), leading candidates to mistakenly choose evasion methods as defining characteristics.
Detailed technical explanation
How to think about this question
In a TCP SYN scan, the attacker sends a SYN packet to each target port. If the port is open, the host responds with SYN-ACK; the attacker then sends RST instead of ACK to abort the handshake. If the port is closed, the host responds with RST. This technique is defined in RFC 793 and is the default scan type in tools like Nmap (-sS). It is often called a 'half-open scan' because no full TCP connection is ever established.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Using TCP SYN packets without completing the three-way handshake. — A is correct because a TCP SYN scan sends a SYN packet to initiate a connection but never completes the three-way handshake by sending the final ACK. This allows the attacker to determine if a port is open (SYN-ACK received) or closed (RST received) without establishing a full connection, which helps evade some logging mechanisms.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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