Refer to the exhibit.

Based on the alert of “Geographically Unusual Remote Access” from Secure Cloud Analytics and the SSH logs from foreign IPs, this device (linux-gcp-east-4c) has likely been compromised. According to SCAZT Section 6: Threat Response (Pages 114–117):

B: Isolating/quarantining the host is an immediate incident response step to prevent lateral movement and data exfiltration.

E: A firewall rule blocking inbound SSH to the GCP VM from external sources would be the appropriate access control response to prevent recurrence.

Options A and C (reinstallation) may be used later during recovery but are not immediate containment steps. Blocking outgoing SSH (Option D) is less relevant than restricting inbound SSH in this scenario.