200-201 Security Concepts Practice Question
A security engineer discovers that an attacker has inserted fake entries into a DNS resolver's cache, redirecting users to a malicious website. Which attack has occurred?
⚠ Common exam trap
Cisco often tests the distinction between DNS poisoning and ARP spoofing by presenting a scenario involving redirection to a malicious site, leading candidates to confuse the Layer 2 ARP attack with the Layer 7 DNS cache corruption.
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
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DNS poisoning
DNS poisoning, also known as DNS cache poisoning, occurs when an attacker inserts forged DNS resource records into a resolver's cache. This causes the resolver to return a malicious IP address for a legitimate domain, redirecting users to an attacker-controlled site without their knowledge.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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DDoS
Why it's wrong here
A DDoS floods a service with traffic to exhaust bandwidth or connection tables; it does not write forged resource records into a resolver's cache. It is tempting because DNS infrastructure is a frequent DDoS target, and volumetric attacks against resolvers would be the correct answer if the symptom were outage rather than redirection.
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DNS poisoning
Why this is correct
DNS poisoning corrupts a resolver's cache with forged records, so subsequent queries return the attacker's IP address and redirect victims. This matches the stem exactly: fake entries inserted into the cache, sending users to a malicious site.
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Man-in-the-middle
Why it's wrong here
Man-in-the-middle interception occurs inline between two communicating parties, whereas cache poisoning corrupts stored records at the resolver itself, affecting all subsequent queries. It is tempting because both redirect victims, and MITM would be correct if the attacker sat on the path altering live traffic.
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ARP spoofing
Why it's wrong here
ARP spoofing poisons layer-2 MAC-to-IP mappings on a local subnet, not the resource records held by a DNS resolver. It is tempting because ARP spoofing also enables redirection, and it would be correct if the attacker had falsified gateway mappings to intercept local traffic.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.