This scenario reflects inappropriate resource usage, a category of network and system misuse defined in the ECIH Network Security Incident module. Excessive outbound traffic during non-business hours combined with high CPU and memory utilization indicates unauthorized or improper use of system resources.

Option A is correct because the behavior suggests activities such as cryptomining, data exfiltration, or unauthorized processing. These activities strain system resources and often occur outside normal working hours to avoid detection.

Option B would not necessarily cause sustained resource strain. Option C focuses on physical changes. Option D relates to permission enforcement, not usage behavior.

ECIH categorizes inappropriate usage as a security incident when system resources are misused in ways that violate policy or threaten availability, making Option A correct.