FRITZ!Box 7581 Service - Knowledge Base

FRITZ!Box 7581 Service

Shared files and printers on a computer are not available over the Internet

You cannot access shared files and printers on remote computers over your FRITZ!Box's Internet connection. It is also not possible to establish connections to Strato HiDrive nor establish other connections using the SMB or CIFS protocol. You also cannot use the SMB/CIFS protocol to establish connections from the Internet to the FRITZ!Box home network.


  • In order to guarantee the security of the computers in the FRITZ!Box home network, in the factory settings the FRITZ!Box blocks all access from the Internet over TCP and UDP ports 139 and 445, which are used for file and printer sharing ("NetBIOS Filter").

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS

1 Configuring the application to access the Internet without NetBIOS

  • Use secure transfer protocols or configure the applications to use secure transfer protocols (for example VPN, HTTPS, SFTP) for accessing the remote computers.

    Note:You can find information on using the application without the SMB/CIFS protocol and the necessary settings in the respective manual, or you can contact the manufacturer directly.


If you cannot or do not want to change the configuration of the application, disable the NetBIOS filter in the FRITZ!Box:

Important:When the NetBIOS filter is disabled, computers in the home network may be subject to more frequent attacks from the Internet. Therefore, set up a firewall on all computers in the home network.

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Filters" in the "Internet" menu.
  3. Click on the "Lists" tab.
  4. Disable the option "NetBIOS filter enabled".
  5. Click "Apply" to save your settings.

Now you can use applications that have to exchange NetBIOS packages with the Internet. This means that you can also access shared files and printers on remote computers using the FRITZ!Box's Internet connection.