Questions: A VPN is primarily used for which of the following purposes? - Allow the use of network-attached printers - Support the distribution of public web documents - Allow remote systems to save on long-distance charges - Support secured communications over an untrusted network

The answer is the fourth one: Support secured communications over an untrusted network.

Explanation for each option:

1. Allow the use of network-attached printers: This is incorrect. While a VPN can facilitate access to network resources like printers, its primary purpose is not specifically to enable the use of network-attached printers.

2. Support the distribution of public web documents: This is incorrect. VPNs are not primarily used for distributing public web documents. Public web documents are typically distributed over the internet without the need for a VPN.

3. Allow remote systems to save on long-distance charges: This is incorrect. While VPNs can enable remote access, they are not specifically designed to save on long-distance charges. The cost savings are more related to using the internet for connectivity rather than traditional long-distance communication methods.

4. Support secured communications over an untrusted network: This is correct. The primary purpose of a VPN (Virtual Private Network) is to provide a secure communication channel over an untrusted network, such as the internet. It encrypts data to protect it from interception and ensures privacy and security for users.

In summary, the main function of a VPN is to ensure secure communications over potentially insecure networks.