- A
Smurf attack
Why wrong: A Smurf attack uses ICMP echo requests with a spoofed source IP to broadcast addresses, causing amplification; the source IP is not necessarily internal.
- B
IP spoofing attack
Correct. The attacker is spoofing the source IP address to appear as an internal host, trying to bypass firewall rules that may allow internal traffic without inspection.
- C
SYN flood
Why wrong: A SYN flood sends many TCP SYN packets without completing handshakes, but the source IPs are often random, not specifically internal.
- D
DNS amplification
Why wrong: DNS amplification uses open DNS resolvers to flood a target with large DNS responses; the source IPs are the resolvers, not internal addresses.
Question 276 of 520
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 is reviewing firewall logs and sees many incoming packets with a source IP address that matches the internal IP range of the company (10.0.0.0/8) arriving on the external interface. Which type of attack is likely being attempted?
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
✓
IP spoofing attack
The correct answer is B because packets arriving on the external interface with a source IP address from the internal 10.0.0.0/8 range indicate that the attacker is forging (spoofing) the source address to impersonate an internal host. This is a classic IP spoofing attack, often used to bypass access control lists or to launch further attacks that rely on trust relationships based on source IP.
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 it's wrong here
A Smurf attack uses ICMP echo requests with a spoofed source IP to broadcast addresses, causing amplification; the source IP is not necessarily internal.
When this WOULD be correct
A Smurf attack would be correct if the question described the attacker sending ICMP echo requests to a network broadcast address with a spoofed source IP of the victim, causing all hosts on that network to reply to the victim, overwhelming it.
- ✓
IP spoofing attack
Why this is correct
Correct. The attacker is spoofing the source IP address to appear as an internal host, trying to bypass firewall rules that may allow internal traffic without inspection.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
SYN flood
Why it's wrong here
A SYN flood sends many TCP SYN packets without completing handshakes, but the source IPs are often random, not specifically internal.
When this WOULD be correct
A SYN flood would be correct if the question described a high volume of incomplete TCP handshakes (SYN packets without final ACK) overwhelming a server, causing denial of service, without mention of source IP matching internal ranges.
- ✗
DNS amplification
Why it's wrong here
DNS amplification uses open DNS resolvers to flood a target with large DNS responses; the source IPs are the resolvers, not internal addresses.
When this WOULD be correct
A DNS amplification attack would be correct if the question described a scenario where the attacker sends small queries to open DNS resolvers with a spoofed victim IP, resulting in large responses flooding the victim. For example: 'A security analyst notices a high volume of DNS responses from external servers to a single internal server, causing bandwidth exhaustion.'
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓IP spoofing attackCorrect answer▾
Why this is correct
Correct. The attacker is spoofing the source IP address to appear as an internal host, trying to bypass firewall rules that may allow internal traffic without inspection.
✗Smurf attackWrong answer — click to see why▾
Why this is wrong here
A Smurf attack uses ICMP echo requests with a spoofed source IP to cause a broadcast storm, but the question describes incoming packets with a source IP matching the internal range on the external interface, which is classic IP spoofing, not a Smurf attack.
★ When this WOULD be the correct answer
A Smurf attack would be correct if the question described the attacker sending ICMP echo requests to a network broadcast address with a spoofed source IP of the victim, causing all hosts on that network to reply to the victim, overwhelming it.
Why candidates choose this
Candidates may confuse any attack involving spoofed IPs with a Smurf attack, or they may recall that Smurf attacks use spoofed source addresses, but they forget the specific mechanism of broadcast amplification.
✗SYN floodWrong answer — click to see why▾
Why this is wrong here
A SYN flood attack involves sending many TCP SYN packets to exhaust server resources, but the question describes packets with a spoofed internal source IP arriving on the external interface, which is characteristic of IP spoofing, not SYN flood.
★ When this WOULD be the correct answer
A SYN flood would be correct if the question described a high volume of incomplete TCP handshakes (SYN packets without final ACK) overwhelming a server, causing denial of service, without mention of source IP matching internal ranges.
Why candidates choose this
Candidates may confuse any flood of packets with a SYN flood, especially when the question mentions 'many incoming packets,' leading them to choose a common DoS attack without analyzing the specific IP spoofing indicator.
✗DNS amplificationWrong answer — click to see why▾
Why this is wrong here
DNS amplification attacks use open DNS servers to amplify traffic to a victim, but they do not involve source IP addresses matching the internal range of the target. The question describes packets with internal IPs arriving externally, which is characteristic of IP spoofing, not DNS amplification.
★ When this WOULD be the correct answer
A DNS amplification attack would be correct if the question described a scenario where the attacker sends small queries to open DNS resolvers with a spoofed victim IP, resulting in large responses flooding the victim. For example: 'A security analyst notices a high volume of DNS responses from external servers to a single internal server, causing bandwidth exhaustion.'
Why candidates choose this
Candidates may confuse any attack involving spoofed IPs with amplification attacks, or they might think that the internal IP range in packets indicates a reflection attack, but DNS amplification specifically uses DNS traffic, not arbitrary packets with internal IPs.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between IP spoofing and other attacks by focusing on the specific packet characteristic (source IP matching internal range on an external interface) rather than the attack's goal or volume, leading candidates to confuse it with a Smurf or SYN flood attack.
Detailed technical explanation
How to think about this question
IP spoofing exploits the fact that IP routing is destination-based and does not inherently validate the source address. In the context of RFC 2827 (BCP 38), ingress filtering at the network edge should drop packets with source addresses that do not belong to the internal network, but if missing, an attacker can send packets that appear to originate from the internal 10.0.0.0/8 range, potentially bypassing ACLs that permit traffic from trusted subnets. Real-world scenarios include using spoofed internal IPs to exploit trust-based services like NFS or RSH, or to hide the true origin of an attack.
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 practitioner preparing for the N10-009 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
What to study next
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FAQ
Questions learners often ask
What does this N10-009 question test?
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: IP spoofing attack — The correct answer is B because packets arriving on the external interface with a source IP address from the internal 10.0.0.0/8 range indicate that the attacker is forging (spoofing) the source address to impersonate an internal host. This is a classic IP spoofing attack, often used to bypass access control lists or to launch further attacks that rely on trust relationships based on source IP.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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