SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
A packet capture from a branch office shows the default gateway IP mapped to a MAC address that does not belong to the router. The same suspicious MAC also answers for the DNS server IP, and gratuitous ARP replies appear every 30 seconds. Which two attacks best match this evidence? Select two.
⚠ Common exam trap
Watch out — candidates often confuse ARP spoofing with a SYN flood or other denial-of-service attacks, failing to recognize that the specific evidence of a mismatched MAC address and gratuitous ARP replies directly points to ARP cache poisoning, not a network-level flood.
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 or poisoning is occurring on the local network.
The evidence shows the default gateway IP is mapped to a MAC address that does not belong to the router, and the same suspicious MAC also answers for the DNS server IP. This is a classic indicator of ARP spoofing or poisoning, where an attacker sends forged ARP replies to associate their MAC address with the IP addresses of critical network devices, such as the gateway and DNS server. Gratuitous ARP replies every 30 seconds further confirm an active ARP poisoning attack, as the attacker repeatedly broadcasts these unsolicited replies to maintain the poisoned ARP cache entries on victim hosts.
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 spoofing or poisoning is occurring on the local network.
Why this is correct
The evidence fits ARP poisoning because an unauthorized MAC address is associating itself with trusted IP addresses such as the gateway and DNS server. Gratuitous ARP replies reinforce the cache manipulation and allow the attacker to redirect traffic at the layer 2 level. This is the classic setup for a local network spoofing attack.
- ✓
A man-in-the-middle interception is likely happening between clients and internal services.
Why this is correct
If the attacker controls address resolution for the gateway and DNS server, client traffic can be forced through the malicious host. That positions the attacker to observe, relay, or modify traffic without immediate detection. The captured symptoms strongly indicate an active man-in-the-middle path rather than only a passive spoofing attempt.
- ✗
The network is experiencing a SYN flood against the gateway.
Why it's wrong here
A SYN flood would show large volumes of half-open TCP sessions and connection-state exhaustion, not ARP cache manipulation. The evidence here is focused on layer 2 address association and forged replies, which does not match a denial-of-service pattern targeting TCP handshake resources.
- ✗
An external host is performing broad port scanning on public services.
Why it's wrong here
Port scanning would appear as repeated connection attempts across many ports or hosts, usually from a source probing for open services. The symptoms here involve local broadcast behavior and cache poisoning, not enumeration of exposed TCP or UDP ports across the perimeter.
- ✗
A password-spraying campaign is targeting remote logins.
Why it's wrong here
Password spraying would produce authentication failures and occasional successful logins, typically in logs from identity providers or VPN systems. It would not explain forged ARP replies or a changed MAC association for the gateway and DNS server. This is a different attack family entirely.
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
Social Engineering Attacks
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.
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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 branch VLAN intermittently reach a fake login page even though DNS records have not changed. A packet capture shows the default gateway MAC address changing every 60 seconds, and the switch logs list repeated unsolicited ARP replies from one workstation. Which attack is most likely?
hard- A.DNS poisoning, because name resolution is directing users to the wrong server.
- ✓ B.ARP poisoning, because forged ARP replies are associating the gateway IP with the attacker's MAC address.
- C.Replay attack, because previously captured traffic is being resent to the network.
- D.Denial of service, because the branch users cannot reliably reach websites.
Why B: The repeated unsolicited ARP replies from one workstation, combined with the default gateway MAC address changing every 60 seconds, directly indicate an ARP poisoning attack. The attacker is sending forged ARP replies to associate the gateway IP with its own MAC address, causing traffic destined for the gateway to be intercepted. This allows the attacker to redirect users to a fake login page without altering DNS records.
Variation 2. Users on the same VLAN report that their browser occasionally reaches a fake internal portal, and packet captures show one host sending forged ARP replies that claim to be the default gateway. Traffic from nearby systems begins flowing through that host. Which attack is occurring?
medium- A.DNS poisoning
- ✓ B.ARP spoofing
- C.MAC flooding
- D.SYN flood
Why B: B is correct because the scenario describes ARP spoofing (also known as ARP poisoning). The attacker sends forged ARP replies to associate their MAC address with the default gateway's IP address, causing traffic from other hosts on the same VLAN to be redirected through the attacker's machine. This allows the attacker to intercept, modify, or redirect traffic to a fake internal portal, which is a classic man-in-the-middle (MITM) attack leveraging the stateless nature of ARP.
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.