200-201 Network Intrusion Analysis Practice Question
During PCAP analysis, a security analyst observes the following pattern: a series of TCP SYN packets to multiple ports on a target, followed by RST packets from the target for closed ports. Which TWO characteristics describe this scan?
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
✓
It is a SYN scan
The SYN scan sends SYN packets and listens for SYN-ACK (open) or RST (closed). It is a stealthy scan because it doesn't complete the TCP handshake.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It uses ICMP echo requests
Why it's wrong here
The pattern involves TCP SYN packets to ports, not ICMP echo requests, which are used by ping sweeps to identify live hosts. It is tempting because ICMP-based discovery is a legitimate reconnaissance technique, and it would be the right answer if the capture showed echo request and echo reply pairs instead of TCP flags.
- ✓
It is a SYN scan
Why this is correct
Sending SYN packets to multiple ports and interpreting RST replies for closed ports is the defining behaviour of a half-open SYN scan, which never completes the handshake. This matches the packet pattern in the stem, distinguishing it from a full-connect scan that completes the three-way handshake.
- ✗
It is a UDP scan
Why it's wrong here
The observed SYN and RST flags are TCP control packets, so the scan is TCP-based, not UDP, which sends connectionless datagrams with no flags. It is tempting because UDP scanning also probes many ports, and that answer would fit if the capture showed UDP datagrams and ICMP port-unreachable responses.
- ✗
It completes the TCP three-way handshake
Why it's wrong here
The capture shows SYN then RST from closed ports, meaning no handshake completes; a half-open scan never reaches the ESTABLISHED state. It is tempting because a TCP connect scan does complete the three-way handshake, and that would be the correct characteristic had the analyst observed SYN-ACK replies followed by ACK.
- ✓
It is a stealthy scan that may avoid logging
Why this is correct
Because the scanner never completes the TCP three-way handshake, the target's application layer never logs the connection attempt, so only SYN and RST packets appear. This half-open behaviour satisfies the stem's requirement for a stealthy scan that may avoid logging.
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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.