Response Operations & Defending Network
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solutions.
A. Evaluate the organization's response to d d d d
the security incident.
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A1. Three Actions the Organization Took in Response to the
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Incident.
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1. Containment: The affected machine (10.1.1.45) was isolated from the network by d d d d d d d d d d
disabling its network port at 10:07.
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2. Eradication & Recovery: The endpoint was restored from a backup at 13:45, and d d d d d d d d d d d d
antivirus (AV) scans were initiated on the HR subnet.
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3. Post-Incident Improvement: Antivirus definitions were updated across all endpoints on d d d d d d d d d
the following day (06/25 at 08:30).
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A2. Evaluation of Effectiveness Using a Recognized
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Framework.
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Using the NIST SP 800-61 Rev. 2 (Computer Security Incident Handling Guide) framework, the
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effectiveness of these actions is evaluated as follows:
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• Action 1 (Containment via Port Disable): Partially Effective. According to NIST,
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containment strategies should be chosen based on the potential for damage and the need
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to preserve evidence. Disabling the switch port was a fast and effective way to
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immediatelystop ongoing data exfiltration or command-and-control (C2) traffic, aligning
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with the goal of minimizing immediate impact. However, the IDS log shows lateral
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movement via SMB from the infected host (10.1.1.45 to 10.1.2.10) at 10:45, which
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occurred after the initial containment at 10:07. This indicates the containment was either
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not fully effective on the first attempt or that a second, compromised host existed. A more
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robust containment strategy is needed.
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• Action 2 (Restoration from Backup & Subnet AV Scan): Effective for Recovery, Inadequate
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for Eradication. NIST emphasizes that eradication must ensure the malicious content is
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completely removed. Restoring from a clean backup is a valid and effective recovery tactic.
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Initiating AV scans on the HR subnet is a good eradication step to find other potential
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infections. However, the procedure relies on "removing known threats," which may not
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catch polymorphic malware or new variants. The focus on the HR subnet, while logical, may
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have missed the lateral movement to the Finance subnet (10.1.2.10), as shown in the IDS
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, log.
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• Action 3 (Organization-wide AV Update): Effective. This is a clear and effective post-
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incident activity that aligns with the NIST "Post-Incident Activity" phase. By updating
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definitions across all endpoints, the organization improves its defensive posture against a
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recurrence of the same threat, strengthening its preparedness for future incidents.
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