Über EFS (Encryption File System)

Das Encrypting File System (EFS), das in den Betriebssystemen Windows 2000, Windows XP (Professional), Windows Server 2003 und Windows Vista (Business, Ultimate, Enterprise) enthalten ist, bietet die Kerntechnologie zur Verschlüsselung, um NTFS-Dateien verschlüsselt auf der Festplatte zu speichern. EFS adressiert insbesondere Sicherheitsprobleme, die durch Tools aufgeworfen werden, die unter anderen Betriebssystemen verfügbar sind und die erlauben, dass Benutzer physisch auf Dateien eines NTFS-Volumes ohne Zugriffsprüfung zugreifen.

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Security features such as logon authentication or file permissions protect network resources from unauthorized access. However, anyone with physical access to a computer such as a stolen laptop can install a new operating system on that computer and bypass the existing operating system's security. In this way, sensitive data can be exposed. Encrypting sensitive files by means of EFS adds another layer of security. When files are encrypted, their data is protected even if an attacker has full access to the computer's data storage.

Only authorized users and designated data recovery agents can decrypt encrypted files. Other system accounts that have permissions for a file — even the Take Ownership permission — cannot open the file without authorization. Even the administrator account cannot open the file if that account is not designated as a data recovery agent. If an unauthorized user tries to open an encrypted file, access is denied.

Benefits of EFS

EFS allows users to store confidential information about a computer when people who have physical access to your computer could otherwise compromise that information, intentionally or unintentionally. EFS is especially useful for securing sensitive data on portable computers or on computers shared by several users. Both kinds of systems are susceptible to attack by techniques that circumvent the restrictions of access control lists (ACLs). In a shared system, an attacker can gain access by starting up a different operating system. An attacker can also steal a computer, remove the hard drive(s), place the drive(s) in another system, and gain access to the stored files. Files encrypted by EFS, however, appear as unintelligible characters when the attacker does not have the decryption key.

Because EFS is tightly integrated with NTFS, file encryption and decryption are transparent. When users open a file, it is decrypted by EFS as data is read from disk. When they save the file, EFS encrypts the data as it is written to disk. Authorized users might not even realize that the files are encrypted because they can work with the files as they normally do.

In its default configuration, EFS enables users to start encrypting files from My Computer with no administrative effort. From the user's point of view, encrypting a file is simply a matter of setting a file attribute. The encryption attribute can also be set for a file folder. This means that any file created in or added to the folder is automatically encrypted.

How EFS Works

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Zusätzliche Informationen sind auf der Microsoft-Website verfügbar:

Und hier ist eine (unvollständige) Liste von Artikeln der Microsoft Knowledge Base mit Bezug auf EFS: