What is an example of encryption at rest?

Encryption at rest refers to the practice of protecting data that is stored on physical devices or within databases, ensuring that it remains confidential even when not actively in use. This is important for safeguarding sensitive information from unauthorized access or breaches.

The encryption of a virtual machine disk serves as a prime example of encryption at rest because it involves encrypting data that resides on disk storage when the virtual machine is powered off or idle. This data is protected from potential threats or unauthorized access while it is stored physically on the disk, thus fulfilling the criteria for encryption at rest.

In contrast, the other options pertain to different aspects of cybersecurity. Encrypting communications with a site-to-site VPN is focused on data in transit, as it secures data being transmitted over a network. Accessing a website via an encrypted HTTPS connection also concerns data in transit, as it protects the communication between the client and the server. Sending an encrypted email pertains to the protection of data while it is being sent, which again involves data in transit rather than data that is stored.

By understanding these distinctions, one can appreciate why encrypting a virtual machine disk is a clear representation of encryption at rest, highlighting how stored data can be effectively secured against unauthorized access.