Disk encryption software
Disk encryption generally refers to wholesale encryption that operates on an entire volume mostly transparently to the user, the system, and applications. This is generally distinguished from file-level encryption that operates by user invocation on a single file or group of files, and which requires the user to decide which specific files should be encrypted. Disk encryption usually includes all aspects of the disk, including directories, so that an adversary cannot determine content, name or size of any file. It is well suited to portable devices such as laptop computers and thumb drives which are particularly susceptible to being lost or stolen. If used properly, someone finding a lost device cannot penetrate actual data, or even know what files might be present.
Disk encryption
Disk encryption does not replace file encryption in all situations. Disk encryption is sometimes used in conjunction with filesystem-level encryption with the intention of providing a more secure implementation. Since disk encryption generally uses the same key for encrypting the whole drive, all data is decryptable when the system runs. However, some disk encryption solutions use multiple keys for encrypting different volumes. If an attacker gains access to the computer at run-time, the attacker has access to all files. Conventional file and folder encryption instead allows different keys for different portions of the disk. Thus an attacker cannot extract information from still-encrypted files and folders.