This scenario involves an active malware incident affecting content integrity, which directly impacts public trust and organizational credibility. According to the ECIH malware response lifecycle, the first priority is containment, not correction or recovery.

Option B is correct because network segregation and isolation prevent the malware from continuing to spread, communicating with command-and-control infrastructure, or further manipulating content. Containment stabilizes the environment and preserves evidence for forensic analysis.

Option C focuses on correction rather than stopping the attack and may allow malware persistence. Option D risks restoring infected components and destroying forensic artifacts. Option A is a communication decision that should follow containment and validation.

ECIH explicitly warns against performing remediation or rollback actions before containment, as doing so may worsen impact or obscure root cause analysis. Isolating compromised systems is therefore the correct immediate response.