The correct answer is a Smurf attack. This is because a Smurf attack exploits IP broadcast addressing and ICMP by sending a large number of ICMP echo request packets with a spoofed source IP—the victim’s address—to a network’s broadcast address, causing every host on that network to reply with ICMP echo replies to the victim. Since the server never sent any echo requests, the unsolicited flood of echo replies is the hallmark of this attack. On the CompTIA Network+ N10-009 exam, this scenario tests your ability to distinguish a Smurf attack from a ping flood or DDoS amplification technique; a common trap is confusing it with a standard ping flood, which originates from a single source. Remember the key clue: the victim receives replies without having sent requests. A useful memory tip is to think “Smurf sends spoofed requests to a broadcast, and the replies Smurf the victim.”
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 a web server is receiving a large number of ICMP echo reply packets from many different external hosts. The server did not send any echo requests. 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.
The Smurf attack uses IP broadcast and spoofing to cause multiple replies to be sent to the victim, creating a flood of ICMP traffic.
B
Ping flood
Why wrong: A ping flood typically involves the attacker sending a high volume of echo requests directly to the target, not receiving replies from many sources.
C
ICMP tunneling
Why wrong: ICMP tunneling is a method to encapsulate data within ICMP packets for covert communication, not a flood attack.
D
Fraggle attack
Why wrong: A Fraggle attack is similar to Smurf but uses UDP echo packets instead of ICMP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Smurf attack
A Smurf attack exploits IP broadcast addressing and ICMP. The attacker sends a large number of ICMP echo request packets with a spoofed source IP (the victim's IP) to a network's broadcast address. All hosts on that network then send ICMP echo reply packets to the victim, overwhelming it with traffic. Since the server never sent any echo requests, the unsolicited flood of echo replies is the hallmark of a Smurf attack.
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.
✓
Smurf attack
Why this is correct
The Smurf attack uses IP broadcast and spoofing to cause multiple replies to be sent to the victim, creating a flood of ICMP traffic.
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.
✗
Ping flood
Why it's wrong here
A ping flood typically involves the attacker sending a high volume of echo requests directly to the target, not receiving replies from many sources.
✗
ICMP tunneling
Why it's wrong here
ICMP tunneling is a method to encapsulate data within ICMP packets for covert communication, not a flood attack.
✗
Fraggle attack
Why it's wrong here
A Fraggle attack is similar to Smurf but uses UDP echo packets instead of ICMP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a Smurf attack (unsolicited replies from many hosts due to a spoofed broadcast request) and a ping flood (direct requests from the attacker to the victim), so candidates mistakenly choose 'ping flood' when they see a flood of ICMP traffic.
Trap categories for this question
Similar concept trap
A Fraggle attack is similar to Smurf but uses UDP echo packets instead of ICMP.
Detailed technical explanation
How to think about this question
The Smurf attack leverages directed broadcast addresses (e.g., 10.0.0.255) which, in older network configurations, would forward the ICMP echo request to every host in the subnet. Each host then replies to the spoofed source IP, creating amplification. Modern routers disable directed broadcast forwarding by default (as per RFC 2644), but the attack can still be attempted on misconfigured networks or via IPv6 multicast abuse. The amplification factor can be as high as the number of hosts in the broadcast domain.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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: Smurf attack — A Smurf attack exploits IP broadcast addressing and ICMP. The attacker sends a large number of ICMP echo request packets with a spoofed source IP (the victim's IP) to a network's broadcast address. All hosts on that network then send ICMP echo reply packets to the victim, overwhelming it with traffic. Since the server never sent any echo requests, the unsolicited flood of echo replies is the hallmark of a Smurf attack.
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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