Explanation
The first step in incident response is to contain the incident activities and attackers, which means preventing them from spreading to other systems or causing more damage. In this case, the security analyst should isolate the instance from the network into quarantine, which means cutting off its communication with other hosts and services. This will stop the cryptocurrency mining activity and prevent the attacker from accessing the instance remotely. Isolating the instance also preserves the evidence for further analysis and investigation.