This CS0-003 practice question tests your understanding of security operations. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. A key principle to apply: dGA (Domain Generation Algorithm) is a C2 technique.. 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 detection engineering phase, Which detection or tuning approach would reduce noise without losing the signal?
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 D is correct because correlating DNS query logs with endpoint process and network connection telemetry provides direct evidence of command-and-control (C2) beaconing. The algorithmically generated domains (DGA) and NXDOMAIN responses are strong indicators of an infected host attempting to contact a C2 server that is currently offline or unreachable. By linking the DNS queries to the specific process generating them and the subsequent network connections, the analyst can confirm malicious activity rather than benign misconfiguration.
Key principle: DGA (Domain Generation Algorithm) is a C2 technique.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Delete the host from the SIEM asset inventory
Why it's wrong here
Removing context makes investigation harder and does not contain the threat.
✗
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.
✓
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 (Domain Generation Algorithm) is a C2 technique.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that NXDOMAIN responses alone are sufficient to confirm C2, when in fact correlation with endpoint and network telemetry is required to distinguish DGA beaconing from legitimate DNS failures or misconfigured clients.
Detailed technical explanation
How to think about this question
DGA-based C2 malware often uses a seed value and a domain generation algorithm to produce a large number of candidate domains daily; the malware attempts to resolve each until it finds one that resolves to a C2 server. The NXDOMAIN responses indicate the C2 server is not currently registered, but the fixed-interval queries reveal the beaconing pattern. Correlating with endpoint process telemetry (e.g., Sysmon Event ID 1 for process creation) can identify the exact executable making the DNS queries, while network connection logs (e.g., NetFlow or Zeek conn logs) show subsequent outbound attempts, confirming the full C2 lifecycle.
KKey Concepts to Remember
DGA (Domain Generation Algorithm) is a C2 technique.
NXDOMAIN responses are common in DGA activity.
Endpoint process telemetry identifies the source of network 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 (Domain Generation Algorithm) is a C2 technique.
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 (Domain Generation Algorithm) is a C2 technique..
What is the correct answer to this question?
The correct answer is: Correlate DNS query logs with endpoint process and network connection telemetry — Option D is correct because correlating DNS query logs with endpoint process and network connection telemetry provides direct evidence of command-and-control (C2) beaconing. The algorithmically generated domains (DGA) and NXDOMAIN responses are strong indicators of an infected host attempting to contact a C2 server that is currently offline or unreachable. By linking the DNS queries to the specific process generating them and the subsequent network connections, the analyst can confirm malicious activity rather than benign misconfiguration.
What should I do if I get this CS0-003 question wrong?
Review dGA (Domain Generation Algorithm) is a C2 technique., then practise related CS0-003 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
DGA (Domain Generation Algorithm) is a C2 technique.
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