mediumMultiple Choice
ISC2 CC Incident Response First Action Practice Question
A medium-sized company uses a SIEM solution to collect logs from firewalls, servers, and endpoints. The security team receives an alert indicating a possible data exfiltration: an employee's workstation is sending large amounts of data to an external IP address outside business hours. The employee works in the finance department and has access to sensitive financial records. The SIEM shows the connection is ongoing. The security team must respond immediately to contain the incident while preserving evidence. The company's incident response plan designates the security team as first responders. Which of the following is the BEST first action?
⚠ Common exam trap
The trap is mistaking delayed containment for a better approach. Immediate isolation (Option A) is prioritized over investigation or notification to prevent further data loss.
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
✓
Block the external IP address at the firewall and disconnect the workstation from the network.
The best first action because it immediately stops the ongoing data exfiltration and isolates the system, containing the incident and preserving evidence. Option B delays containment, Option C may alert a potential insider threat, and Option D should be performed after containment to avoid further data loss.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Block the external IP address at the firewall and disconnect the workstation from the network.
Why this is correct
Blocking the external IP at the firewall and isolating the workstation halts ongoing exfiltration immediately, satisfying the containment requirement. The workstation remains intact and unpowered-off, preserving volatile memory and forensic artefacts for later evidence collection.
- ✗
Notify the employee's manager and wait for further instructions.
Why it's wrong here
Manager notification introduces delay while exfiltration continues, and the manager lacks authority to direct first-responder containment actions. The plan designates the security team as responders, so escalation should follow containment. This step belongs in post-incident communication, not as the immediate action.
- ✗
Call the employee to ask if they are transferring files for a legitimate business purpose.
Why it's wrong here
Contacting the suspected employee tips off a possible insider, allowing them to destroy evidence or accelerate the transfer, and the ongoing session remains active. Verification via the user is not containment. This approach fits low-confidence alerts where no active data flow or insider access is indicated.
- ✗
Take a forensic image of the workstation's hard drive before anything else.
Why it's wrong here
Imaging the drive first leaves the ongoing external connection running, so data continues leaving the network during acquisition. Containment must stop the transfer before volatile evidence is lost. Forensic imaging is appropriate once the threat is isolated, not as the opening action.
Go deeper
Related to this question
Learn chapter
Business Continuity and Disaster Recovery
Key term
SIEM
SIEM (Security Information and Event Management) is a system that collects and analyzes log data from across an IT environment to detect and respond to security threats in real time.
Key term
Incident
An incident is a security event that violates an organization's policies or threatens its data, systems, or operations, requiring a structured response.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC practice question is part of Courseiva's free ISC2 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 CC exam.