Quick Answer
The correct answer is a SYN flood attack. This is because a SYN flood exploits the TCP three-way handshake by deluging a server with SYN packets from a spoofed or external IP, but never sending the final ACK to complete the connection. Each half-open connection consumes a slot in the server’s backlog queue, quickly exhausting resources and blocking legitimate traffic—exactly what the log evidence of excessive SYN packets with no handshake completion reveals. On the ISC2 Certified in Cybersecurity CC exam, this question tests your ability to map network-layer symptoms to attack types, often appearing in scenario-based log analysis items. A common trap is confusing this with a ping flood or DDoS, but the key differentiator is the incomplete handshake. For a quick memory tip, think “SYN sent, ACK absent” to recall that the attack relies on never finishing the three-way handshake.
This CC 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 engineer is reviewing logs and notices that an internal server is receiving excessive SYN packets from an external IP, but never completing the three-way handshake. What type of attack is likely occurring?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "never"
Why it matters: Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
Smurf attack
Why wrong: Smurf attack uses ICMP broadcast amplification.
Ping of death
Why wrong: Ping of death involves oversized ICMP packets.
ARP poisoning
Why wrong: ARP poisoning maps IPs to MAC addresses locally.
SYN flood
SYN flood sends many SYN packets, leaving half-open connections.
Answer choices
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 server without completing the handshake (i.e., not sending the final ACK). This exhausts the server's connection table resources, preventing legitimate connections. The log evidence—excessive SYN packets from an external IP with no handshake completion—is the classic signature of a SYN flood.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Smurf attack
Why it's wrong here
Smurf attack uses ICMP broadcast amplification.
Ping of death
Why it's wrong here
Ping of death involves oversized ICMP packets.
ARP poisoning
SYN flood
Why this is correct
SYN flood sends many SYN packets, leaving half-open connections.
Clue confirmation
The clue word "never" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
ISC2 often tests the distinction between attacks that use ICMP (Smurf, Ping of death) versus TCP (SYN flood), so candidates may confuse the protocol layer or misremember that a Smurf attack involves SYN packets instead of ICMP echo requests.
Detailed technical explanation
Under the hood, a SYN flood targets the server's 'listen backlog'—the queue of half-open connections (SYN_RCVD state). The server allocates memory for each incomplete handshake, and once the backlog fills (default often 128 or 256 in Linux), new connection requests 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. In a real-world scenario, attackers often spoof the source IP to avoid detection and make filtering harder.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
What to study next
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FAQ
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
The correct answer is: SYN flood — A SYN flood attack exploits the TCP three-way handshake by sending a high volume of SYN packets to a target server without completing the handshake (i.e., not sending the final ACK). This exhausts the server's connection table resources, preventing legitimate connections. The log evidence—excessive SYN packets from an external IP with no handshake completion—is the classic signature of a SYN flood.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "never". Absolute qualifier. True only if the statement has zero exceptions — be cautious of options that seem obvious but break down in edge cases.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CC practice question is part of Courseiva's free ISC2 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 CC exam.
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