easyMultiple ChoiceObjective-mapped
ISC2 CC Practice Question: A security analyst is reviewing an alert from the…
A security analyst is reviewing an alert from the IDS that shows a large number of TCP SYN packets sent to a single port on multiple internal hosts from a single external IP address. The analyst suspects a reconnaissance attack. Which type of attack is this most likely?
⚠ Common exam trap
ISC2 often tests the distinction between a SYN flood (DoS) and a SYN scan (reconnaissance), and the trap here is that candidates confuse the use of SYN packets in a volumetric attack versus a probing technique.
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
✓
SYN scan
This is most likely a SYN scan (option D), a reconnaissance technique where an attacker sends TCP SYN packets to a specific port on multiple hosts to determine if the port is open. A SYN scan is stealthier than a full TCP connect scan because it never completes the three-way handshake, leaving fewer logs. The IDS alert describes the hallmark behavior of a SYN scan: a single external IP targeting the same port across many internal hosts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SYN flood
Why it's wrong here
A SYN flood aims to overwhelm the target with half-open connections, not just scan.
- ✗
Ping sweep
Why it's wrong here
A ping sweep uses ICMP echo requests to identify live hosts, not TCP SYN packets.
- ✗
Smurf attack
Why it's wrong here
A Smurf attack uses ICMP echo replies to amplify traffic, not TCP SYN packets.
- ✓
SYN scan
Why this is correct
A SYN scan sends TCP SYN packets to determine which ports are open, characteristic of reconnaissance.
Visual reference
Go deeper
Related to this question
Learn chapter
Introduction to Security Principles
Key term
IDS
An IDS is a security system that monitors network or system traffic for suspicious activity and alerts administrators to potential threats, but does not actively block them.
Key term
Alert
An alert is a notification that something unusual or potentially harmful has happened in a computer system or network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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