(EFS) A feature in the Windows operating system that enables users to encrypt files and folders on an NTFS volume disk to keep them safe from access by intruders.

Abbreviated to EFS, a Windows 2000 file system that enables users to encrypt files and folders on an NTFS partition or volume. It protects files from unauthorized access because each file is encrypted using a randomly generated key.

A new feature in Windows 2000 that protects sensitive data in files that are stored on disk using the NTFS file system. It uses symmetric key encryption in conjunction with public key technology to provide confidentiality for files. It runs as an integrated system service, which makes EFS easy to manage, difficult to attack, and transparent to the file owner and to applications.