Quick Answer
The primary risk of isolating a domain controller during incident containment is the loss of authentication services. This occurs because a domain controller is the authoritative source for identity verification in Active Directory, handling Kerberos and NTLM authentication requests. When you cut its network access, it can no longer process logins, resource access, or group policy updates, effectively halting all user and system authentication across the domain. On the ISC2 Certified in Cybersecurity CC exam, this question tests your understanding of the containment phase’s trade-offs: while isolating a compromised server limits lateral movement, isolating a domain controller creates a critical service outage. A common trap is focusing on data loss or malware spread, but the primary risk is always the immediate breakdown of identity verification. Remember the mnemonic “DC = Door Controller” — if you lock the door controller away, nobody can get in or out.
This CC practice question tests your understanding of business continuity, dr & incident response. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
An organization's incident response plan specifies containment, eradication, and recovery phases. During containment, the team isolates a compromised server from the network. However, the server is a domain controller. What is the PRIMARY risk of this action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Data loss on the server
Why wrong: Data may be preserved, but loss of services is more urgent.
Violation of chain of custody
Why wrong: Chain of custody relates to evidence handling, not immediate service impact.
Propagation of malware to other systems
Why wrong: Isolation actually prevents propagation.
Loss of authentication services
Domain controllers provide authentication; isolating them disrupts network logins.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Loss of authentication services
Isolating a domain controller from the network prevents it from processing authentication requests (Kerberos and NTLM), which halts user logins, resource access, and group policy updates across the domain. This loss of authentication services is the primary risk because the domain controller is the authoritative source for identity verification in Active Directory.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Data loss on the server
Why it's wrong here
Data may be preserved, but loss of services is more urgent.
Violation of chain of custody
Why it's wrong here
Chain of custody relates to evidence handling, not immediate service impact.
Propagation of malware to other systems
Why it's wrong here
Isolation actually prevents propagation.
Loss of authentication services
Why this is correct
Domain controllers provide authentication; isolating them disrupts network logins.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates may focus on the general containment goal of stopping malware spread (Option C) rather than recognizing that isolating a domain controller specifically cripples the authentication infrastructure, which is the most critical and immediate risk.
Detailed technical explanation
When a domain controller is isolated, clients cannot obtain Kerberos ticket-granting tickets (TGTs) or service tickets, and cached credentials may expire, leading to complete authentication failure. In a real-world scenario, if the domain controller hosts FSMO roles (e.g., PDC emulator), isolation can also cause time synchronization issues and password change failures across the domain.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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FAQ
Business Continuity, DR & Incident Response — This question tests Business Continuity, DR & Incident Response — Read the scenario before looking for a memorised answer..
The correct answer is: Loss of authentication services — Isolating a domain controller from the network prevents it from processing authentication requests (Kerberos and NTLM), which halts user logins, resource access, and group policy updates across the domain. This loss of authentication services is the primary risk because the domain controller is the authoritative source for identity verification in Active Directory.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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