200-201 Security Concepts Practice Question
A security analyst at a retail company is reviewing DNS logs and notices a workstation repeatedly resolving random-looking subdomains such as a8f3k2.example-bad.com, followed by a long TXT record response containing encoded data. No user reported visiting any website. Which technique is most likely occurring?
⚠ Common exam trap
The trap here is assuming any random-looking domain name must be a domain generation algorithm, when the oversized TXT responses reveal a covert tunneling channel rather than simple DGA beaconing.
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
✓
DNS tunneling used for command-and-control or data exfiltration
Random subdomains plus oversized TXT replies from a single workstation indicate DNS tunneling, a covert channel that abuses port 53 to move data or commands past egress controls. Because DNS is almost always permitted, attackers use it for command-and-control and exfiltration. The analyst should isolate the host, capture full DNS traffic, and inspect the resolver logs for the encoded payload pattern.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
DNS tunneling used for command-and-control or data exfiltration
Why this is correct
The high volume of unique, algorithmically generated subdomains combined with large TXT responses is characteristic of DNS tunneling, where an attacker encodes data or commands inside DNS queries and responses to bypass egress filtering. Legitimate DNS rarely produces this pattern, so the analyst should treat this host as compromised and begin containment.
- ✗
Cache poisoning of the local resolver to redirect the workstation to a malicious site
Why it's wrong here
Cache poisoning injects false records so that many clients resolve a legitimate name to an attacker-controlled address. The scenario shows many unique random subdomains with encoded TXT answers tied to one host, which is exfiltration-style tunneling, not corruption of cached records for a shared domain name.
- ✗
A domain generation algorithm used only for load balancing legitimate traffic
Why it's wrong here
Domain generation algorithms do create random-looking domains, but legitimate load balancing does not rely on DGA-style names paired with oversized TXT payloads. The encoded TXT data indicates bidirectional covert communication rather than distribution of normal user requests, so this explanation does not fit the observed behavior on the workstation.
- ✗
A DNS amplification attack targeting the internal recursive resolver
Why it's wrong here
DNS amplification floods a victim with large responses by spoofing the victim's source address against open resolvers. Here the queries originate from an internal workstation receiving the large responses itself, which indicates a covert channel from that host rather than a reflection attack aimed at the resolver or a third party.
Visual reference
Go deeper
Related to this question
About these practice questions
This 200-201 question is part of Courseiva's 968-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 →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.