SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
Several users on the same subnet report intermittent inability to reach the default gateway. A packet capture shows ARP replies mapping the gateway IP to a different MAC address, and the same host keeps sending those replies every few seconds. What attack is most likely?
⚠ Common exam trap
Watch out — candidates often confuse ARP spoofing with a man-in-the-middle attack in general, but the question specifically describes ARP-level manipulation (forged ARP replies mapping the gateway IP to a different MAC), which is the defining characteristic of ARP spoofing, not a TLS downgrade or replay attack.
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
✓
ARP spoofing
ARP spoofing. The symptoms—intermittent gateway unreachability, ARP replies mapping the gateway IP to a different MAC address, and repeated unsolicited ARP replies—are classic indicators of an ARP spoofing (also called ARP poisoning) attack. The attacker sends forged ARP replies to associate their own MAC address with the gateway IP, causing traffic destined for the gateway to be sent to the attacker instead, disrupting connectivity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replay attack
Why it's wrong here
A replay attack involves capturing legitimate network traffic and retransmitting it to achieve unauthorized actions or duplicate effects. However, the observed false ARP replies on the local subnet are not a matter of reusing old packets; they reflect an active fabrication of link-layer address mappings. The users' intermittent connectivity stems from poisoned ARP caches, not from replayed data, so replay does not align with the evidence.
- ✓
ARP spoofing
Why this is correct
ARP spoofing, or ARP poisoning, occurs when an attacker sends unsolicited ARP replies or gratuitous ARP packets to associate the gateway's IP address with the attacker's MAC address. This causes hosts on the subnet to update their ARP caches, redirecting traffic meant for the gateway to the attacker, who can then sniff, intercept, or drop packets. The resulting false ARP entries explain the users' intermittent inability to communicate, as traffic is misdirected at the data-link layer.
- ✗
DNS amplification
Why it's wrong here
DNS amplification is a reflection-based distributed denial-of-service technique where the attacker sends small queries with a spoofed victim source address to open DNS resolvers, which then send large responses to the victim, overwhelming its bandwidth. It does not involve forging ARP replies or altering MAC-to-IP mappings on a local subnet. Since the question specifically notes false ARP information, DNS amplification cannot be the cause, as it operates at the application layer and relies on DNS infrastructure.
- ✗
Man-in-the-middle via TLS downgrade
Why it's wrong here
A man-in-the-middle attack via TLS downgrade relies on manipulating the client and server's cryptographic handshake to force the use of weaker, less secure encryption algorithms. This attack would occur during the TLS negotiation process and would not produce forged ARP replies or corrupt the ARP cache of local hosts. The capture's evidence of false ARP mappings points to a Layer 2 address-spoofing attack rather than a flaw in TLS protocol negotiation.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Threat Intelligence and Indicators of Compromise
Key term
ARP poisoning
ARP poisoning is a network attack where an attacker sends fake Address Resolution Protocol messages to link their MAC address with a legitimate IP address, enabling them to intercept, modify, or stop data on a local network.
Key term
ARP
Address Resolution Protocol (ARP) is a network protocol used to map a device's IP address to its physical MAC address so data can be delivered correctly on a local network.
About these practice questions
This SY0-701 question is part of Courseiva's 1,013-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on SY0-701
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Users on a wired subnet report intermittent outages when reaching an internal application. A packet capture shows the default gateway IP address repeatedly mapped to a different workstation MAC address, and traffic is being forwarded through that workstation. What attack is most likely occurring?
medium- A.DNS poisoning, because the hostname is resolving to the wrong server.
- ✓ B.ARP spoofing, because false Layer 2 address mappings are redirecting traffic.
- C.Replay attack, because packets are being resent to the gateway.
- D.Rogue DHCP service, because clients are losing access to the default gateway.
Why B: B is correct because ARP spoofing (also known as ARP poisoning) involves an attacker sending forged ARP messages over a local area network. This results in the attacker's MAC address being associated with the IP address of the default gateway, causing traffic destined for the gateway to be forwarded to the attacker's workstation instead. The packet capture evidence of the default gateway IP repeatedly mapped to a different workstation MAC address is the classic signature of this attack.
Variation 2. Several users on the same subnet report that their traffic to the default gateway is intermittently slow and sometimes reaches the wrong device. A packet capture shows ARP replies that map the gateway IP to a different MAC address. What attack is most likely occurring?
easy- ✓ A.ARP spoofing, which poisons address resolution on the local network
- B.DNS amplification, which overwhelms the target with reflected DNS traffic
- C.Replay attack, which resends captured authentication data
- D.Port scanning, which probes hosts for open services and ports
Why A: ARP spoofing (also known as ARP poisoning) is the correct answer because the attacker sends forged ARP replies that associate the default gateway's IP address with the attacker's MAC address. This causes the victims' ARP caches to update with the false mapping, so traffic destined for the gateway is instead sent to the attacker, leading to intermittent connectivity and misrouted packets. The symptoms—slow traffic and reaching the wrong device—are classic indicators of a man-in-the-middle (MITM) attack via ARP cache poisoning. (Switches maintain MAC address tables, not ARP caches.)
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SY0-701 practice question is part of Courseiva's free CompTIA 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 SY0-701 exam.