The answer is ARP poisoning, also known as ARP spoofing. This attack is correct because the attacker sends unsolicited ARP replies that fraudulently associate the default gateway’s IP address with the attacker’s own MAC address, overwriting the legitimate ARP cache entries on victim hosts. As a result, traffic intended for the gateway is redirected through the attacker’s workstation, causing intermittent connectivity when the attacker forwards or drops packets. On the Security+ SY0-701 exam, this scenario tests your understanding of Layer 2 attacks and how ARP’s lack of authentication enables man-in-the-middle redirection. A common trap is confusing ARP poisoning with MAC flooding, but remember: ARP poisoning corrupts the IP-to-MAC mapping, while MAC flooding overwhelms the switch’s CAM table. Memory tip: “Unsolicited ARP = Unwanted Spoofing” — if you see repeated, unsolicited ARP replies mapping a gateway IP to a different MAC, think ARP poisoning.
SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
This SY0-701 practice question tests your understanding of threats, vulnerabilities, and mitigations. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
Several users on the same subnet report intermittent loss of access to the default gateway. A packet capture shows repeated unsolicited ARP replies mapping the gateway IP address to a different MAC address. Traffic is occasionally sent through an unknown workstation. What 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ARP poisoning
The attack is ARP poisoning (also known as ARP spoofing). The attacker sends unsolicited ARP replies to associate the gateway's IP address with the attacker's MAC address, causing traffic destined for the gateway to be redirected through the attacker's workstation. This results in intermittent connectivity as the attacker can forward or drop packets, and the repeated unsolicited replies overwrite the legitimate ARP cache entries on the victim hosts.
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.
✓
ARP poisoning
Why this is correct
ARP poisoning forges address resolution replies so victims map the gateway IP to the attacker MAC.
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.
✗
DNS cache poisoning
Why it's wrong here
DNS cache poisoning alters name-to-IP records, not Layer 2 ARP mappings on a local subnet.
✗
Replay attack
Why it's wrong here
A replay attack reuses captured authentication or transaction data, which is not what the capture shows.
✗
Amplification attack
Why it's wrong here
Amplification floods a target using reflected traffic, not forged ARP responses on a LAN.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing ARP poisoning with DNS cache poisoning because both involve 'poisoning' a cache, but ARP operates at Layer 2 (MAC addresses) while DNS operates at Layer 7 (domain names), and the symptoms of intermittent gateway access and unsolicited ARP replies are unique to ARP attacks.
Trap categories for this question
Command / output trap
A replay attack reuses captured authentication or transaction data, which is not what the capture shows.
Detailed technical explanation
How to think about this question
ARP is a stateless protocol; hosts accept unsolicited ARP replies even without a corresponding request, which is the vulnerability exploited in ARP poisoning. Tools like Ettercap or arpspoof send crafted packets to update the ARP cache of each victim, enabling man-in-the-middle attacks. In a real-world scenario, an attacker could silently intercept and modify traffic between users and the default gateway, capturing credentials or injecting malicious content.
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 analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SY0-701 question in full detail.
Threats, Vulnerabilities, and Mitigations — This question tests Threats, Vulnerabilities, and Mitigations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ARP poisoning — The attack is ARP poisoning (also known as ARP spoofing). The attacker sends unsolicited ARP replies to associate the gateway's IP address with the attacker's MAC address, causing traffic destined for the gateway to be redirected through the attacker's workstation. This results in intermittent connectivity as the attacker can forward or drop packets, and the repeated unsolicited replies overwrite the legitimate ARP cache entries on the victim hosts.
What should I do if I get this SY0-701 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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