SYN Flood Attack: Detection and Analysis
A security analyst notices that a server is sending an unusually high number of SYN packets to multiple external hosts, but the connections are never completed. The server is most likely involved in which type of attack?
Quick Answer
The correct answer is a SYN flood attack because the server is sending a high volume of SYN packets without completing the TCP three-way handshake, which is the hallmark of this denial-of-service technique. In a SYN flood, the attacker’s machine bombards a target with initial connection requests, exhausting the target’s backlog queue by never sending the final ACK, leaving half-open connections that consume resources. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of TCP state exhaustion and the distinction between being the victim versus the source of an attack—a common trap is assuming the server is under attack when it is actually the launch point. Memory tip: think of the “half-open handshake” as a handshake that never shakes back—SYN sent, SYN-ACK received, but no final ACK, leaving the target hanging.
⚠ Common exam trap
The CEH exam often tests the distinction between the attacker's role (sending SYN packets) and the victim's role (receiving them), so candidates may mistakenly think the server is the victim of a SYN flood rather than the source of the 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
✓
SYN flood
A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets to a target without completing the handshake (no final ACK). The server in this scenario is the attacker, generating these incomplete SYN connections to exhaust the target's resources, such as the SYN backlog queue, leading to denial of service.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Ping of Death
Why it's wrong here
Ping of Death sends oversized ICMP packets, not SYN packets.
- ✗
Smurf attack
Why it's wrong here
Smurf uses ICMP echo requests to broadcast addresses, not SYN packets.
- ✗
UDP flood
Why it's wrong here
UDP flood uses UDP packets, not TCP SYN packets.
- ✓
SYN flood
Why this is correct
Correct. A SYN flood sends many SYN packets with no final ACK, overwhelming the target.
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Same concept, more angles
1 more way this is tested on CEH
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security analyst notices repeated TCP SYN packets sent to a server without corresponding SYN-ACK replies. The source IP addresses are spoofed and appear to be random. Which type of attack is MOST likely occurring?
medium- ✓ A.SYN flood
- B.UDP flood
- C.ICMP flood
- D.Ping of Death
Why A: A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets with spoofed source IP addresses to a target server. The server responds with SYN-ACK packets to the spoofed addresses, which never complete the handshake, causing the server to exhaust its memory and CPU resources by maintaining half-open connections. This matches the described behavior of repeated SYN packets without corresponding SYN-ACK replies.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CEH practice question is part of Courseiva's free EC-Council 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 CEH exam.