Encryption of data at rest means converting the information on a storage device into a form that cannot be understood by anyone who does not have the key to decode it. This protects the information in case the device is lost, stolen, or accessed by unauthorized individuals. Formatting just erases data, but does not necessarily protect it from being recovered by savvy attackers. Password protection can help prevent access to a device, but it does not protect the data itself if the device is compromised. A firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization's previously established security policies and therefore does not apply to data at rest directly.