The answer is a SYN flood attack. This is correct because a SYN flood exploits the TCP three-way handshake by sending a massive volume of SYN packets—often from a spoofed or single source IP—without ever completing the final ACK step. The server dutifully allocates memory and resources for each half-open connection, rapidly exhausting its connection table and denying service to legitimate users. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of how denial-of-service attacks target the handshake process; a common trap is confusing it with a ping flood or Smurf attack, which use ICMP rather than TCP. To remember, think of the three-way handshake as a handshake that never finishes—SYN sent, SYN-ACK replied, but no ACK returned. A simple memory tip: “SYN sent, resources spent.”
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. 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.
A security analyst notices that the company's web server is receiving a high volume of TCP SYN packets from a single source IP address, but the server is not completing the three-way handshake. Which type of attack is most likely occurring?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Correct. A SYN flood is a DoS attack that sends numerous SYN packets, leaving half-open connections and consuming server resources.
B
B) Smurf attack
Why wrong: Incorrect. A Smurf attack uses ICMP echo requests to a broadcast address, causing all hosts to reply to the victim. It does not involve TCP SYN packets.
C
C) Ping of death
Why wrong: Incorrect. A Ping of death sends an oversized ICMP packet that causes a buffer overflow. It does not use TCP SYN packets.
D
D) ARP poisoning
Why wrong: Incorrect. ARP poisoning involves sending fake ARP replies to intercept traffic, not sending TCP SYN packets to a server.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A) SYN flood
A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets from a spoofed or single source IP without completing the handshake. The server allocates resources for each half-open connection, eventually exhausting its connection table and denying service to legitimate users. This matches the scenario where the server receives many SYN packets but never completes the handshake.
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.
✓
A) SYN flood
Why this is correct
Correct. A SYN flood is a DoS attack that sends numerous SYN packets, leaving half-open connections and consuming server resources.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
B) Smurf attack
Why it's wrong here
Incorrect. A Smurf attack uses ICMP echo requests to a broadcast address, causing all hosts to reply to the victim. It does not involve TCP SYN packets.
✗
C) Ping of death
Why it's wrong here
Incorrect. A Ping of death sends an oversized ICMP packet that causes a buffer overflow. It does not use TCP SYN packets.
✗
D) ARP poisoning
Why it's wrong here
Incorrect. ARP poisoning involves sending fake ARP replies to intercept traffic, not sending TCP SYN packets to a server.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between a SYN flood and a Smurf attack by describing a flood of packets from a single source—candidates confuse the ICMP-based Smurf attack with the TCP-based SYN flood because both involve flooding, but the protocol and mechanism are completely different.
Detailed technical explanation
How to think about this question
In a SYN flood, the attacker sends SYN packets with a spoofed source IP (often unroutable or non-existent) so the server's SYN-ACK responses go unanswered, leaving connections in a half-open state. The server's backlog queue (e.g., net.core.somaxconn in Linux) fills up, and once full, new legitimate SYN packets are dropped. Modern mitigations include SYN cookies (RFC 4987), which encode connection state in the SYN-ACK sequence number, avoiding resource allocation until the handshake completes.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A) SYN flood — A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets from a spoofed or single source IP without completing the handshake. The server allocates resources for each half-open connection, eventually exhausting its connection table and denying service to legitimate users. This matches the scenario where the server receives many SYN packets but never completes the handshake.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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