CS0-003 Practice Question: DGA activity often results in high NXDOMAIN rates.
This CS0-003 practice question tests your understanding of security operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: dGA activity often results in high NXDOMAIN rates.. 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.
A SOC analyst reviews DNS telemetry and sees a workstation resolving hundreds of algorithmically generated domains at fixed intervals, with most responses returning NXDOMAIN. What evidence should the analyst prioritize to validate command-and-control beaconing? In the containment trade-off phase, Which response balances containment with evidence preservation?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Correlate DNS query logs with endpoint process and network connection telemetry
Option A is correct because correlating DNS query logs with endpoint process and network connection telemetry directly validates command-and-control (C2) beaconing. The algorithmically generated domains (AGDs) and NXDOMAIN responses are classic indicators of a domain generation algorithm (DGA) attempting to resolve a C2 server that may be offline or blocked. By linking the DNS queries to specific processes and network connections on the endpoint, the analyst can confirm whether the workstation is executing malicious code that generates these queries, rather than benign software or a false positive.
Key principle: DGA activity often results in high NXDOMAIN rates.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Correlate DNS query logs with endpoint process and network connection telemetry
Why this is correct
The pattern is suspicious, but process and connection context shows whether a host process is repeatedly attempting outbound C2 communication.
Related concept
DGA activity often results in high NXDOMAIN rates.
✗
Search only for successful HTTP 200 responses
Why it's wrong here
DGA activity may fail resolution frequently, so HTTP status codes alone miss the behaviour.
✗
Block all DNS traffic from the subnet
Why it's wrong here
Immediate blanket blocking may disrupt operations and does not validate the source process.
✗
Delete the host from the SIEM asset inventory
Why it's wrong here
Removing context makes investigation harder and does not contain the threat.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that NXDOMAIN responses are irrelevant or that blocking all traffic is a safe containment step, when in reality the key is to correlate multiple data sources to confirm malicious activity without prematurely destroying evidence.
Detailed technical explanation
How to think about this question
DGA-based C2 malware, such as Conficker or TrickBot, generates thousands of pseudo-random domains per day, attempting to resolve each one until a successful response is received. The NXDOMAIN responses are expected when the registered C2 domain is not yet live or has been sinkholed by a security vendor. Correlating DNS query logs with endpoint process telemetry (e.g., via Sysmon Event ID 1 or Windows Event Log 4688) allows the analyst to identify the specific executable (e.g., svchost.exe running from a non-standard path) that is generating the queries, while network connection logs (e.g., NetFlow or EDR connection events) reveal the actual IP addresses and ports used for any successful C2 communication.
KKey Concepts to Remember
DGA activity often results in high NXDOMAIN rates.
Correlation of multiple telemetry sources is critical for C2 validation.
Endpoint process telemetry identifies the source of suspicious activity.
→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
DGA activity often results in high NXDOMAIN rates.
Real-world example
How this comes up in practice
A SOC analyst notices unusual lateral movement in the network at 2 AM. The IR playbook dictates: identify and contain (isolate the affected machine), then eradicate (remove the malware), then recover (restore from backup), then document. Skipping containment before eradication risks the attacker regaining access. Questions like this test the sequence and rationale of incident response phases.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CS0-003 question in full detail.
Security Operations — This question tests Security Operations — DGA activity often results in high NXDOMAIN rates..
What is the correct answer to this question?
The correct answer is: Correlate DNS query logs with endpoint process and network connection telemetry — Option A is correct because correlating DNS query logs with endpoint process and network connection telemetry directly validates command-and-control (C2) beaconing. The algorithmically generated domains (AGDs) and NXDOMAIN responses are classic indicators of a domain generation algorithm (DGA) attempting to resolve a C2 server that may be offline or blocked. By linking the DNS queries to specific processes and network connections on the endpoint, the analyst can confirm whether the workstation is executing malicious code that generates these queries, rather than benign software or a false positive.
What should I do if I get this CS0-003 question wrong?
Review dGA activity often results in high NXDOMAIN rates., then practise related CS0-003 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
DGA activity often results in high NXDOMAIN rates.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This CS0-003 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 CS0-003 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.