“The Encrypting File System (EFS) on Microsoft Windows is a feature introduced in version 3.0 of NTFS that provides filesystem-level encryption. The technology enables files to be transparently encrypted to protect confidential data from attackers with physical access to the computer.

EFS is enabled in all versions of Windows meant for professional use from Windows 2000 onwards. However, since significant caveats exist for its use, no files are encrypted by default and must explicitly be invoked by the user (in organizational settings encryption can also be mandated through Group Policy).” Read more.