A department allows multiple users to perform maintenance on a system using a single set...

Multi-factor authentication is the most effective way to mitigate the risk of unauthorized access to the system, as it requires the users to provide more than one piece of evidence to prove their identity, such as a password, a token, a biometric feature, etc. This reduces the likelihood of compromising the credentials and ensures that only authorized users can perform maintenance on the system.

Single sign-on is a convenience feature that allows users to access multiple systems with one set of credentials, but it does not address the risk of sharing credentials among multiple users.

Audit trail review is a detective control that can help identify and investigate unauthorized access to the system, but it does not prevent or mitigate the risk of credential compromise.

Data encryption at rest is a security measure that protects the data stored on the system from unauthorized access, but it does not prevent or mitigate the risk of credential compromise. References = CRISC Review Manual, 7th Edition, ISACA, 2020, page 107-108.