200-201 Security Monitoring Practice Question
Which OSI layer is targeted by a TCP SYN flood attack?
⚠ Common exam trap
Cisco often tests the distinction between the layer where the vulnerability exists (Layer 4, TCP) versus the layer where the packet is encapsulated (Layer 3, IP), leading candidates to mistakenly choose Layer 3 because the attack uses IP packets.
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
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Layer 4 - Transport
A TCP SYN flood attack targets the Transport layer (Layer 4) because it exploits the TCP three-way handshake mechanism. The attacker sends a high volume of SYN packets with spoofed source IP addresses, causing the server to allocate resources for half-open connections that never complete, exhausting its connection queue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Layer 7 - Application
Why it's wrong here
A SYN flood exploits the TCP three-way handshake, which operates at Layer 4 (Transport), not the Application layer. Layer 7 is tempting because application-layer attacks such as HTTP floods also exhaust connections, but they target request processing rather than half-open TCP session state.
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Layer 4 - Transport
Why this is correct
TCP operates at Layer 4, where SYN floods exhaust the connection table by sending numerous half-open handshakes. The attack targets the transport-layer three-way handshake mechanism itself, so Layer 4 is the precise target rather than the application payload or network routing.
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Layer 3 - Network
Why it's wrong here
A SYN flood exhausts TCP half-open connection tables at Layer 4 (Transport); IP addressing and routing at Layer 3 are untouched. Layer 3 is tempting because ICMP floods and IP fragmentation attacks genuinely operate there, but they abuse packet delivery rather than TCP session establishment.
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Layer 2 - Data Link
Why it's wrong here
SYN floods consume Transport-layer (Layer 4) connection state, not Data Link framing. Layer 2 is tempting because MAC flooding and ARP spoofing genuinely attack switching and addressing there, but those manipulate frame forwarding rather than exhausting TCP handshake queues.
Visual reference
About these practice questions
Courseiva writes every 200-201 question from scratch — 968 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.