Which of the following best describes a VPN?

A VPN, or Virtual Private Network, is best described as a private network built using public infrastructure. This definition highlights how a VPN creates a secure connection over the internet, allowing users to send and receive data as if their devices were directly connected to a private network.

When using a VPN, data is encrypted, which provides confidentiality and protects it from interception while traveling over public networks. This makes VPNs particularly useful for ensuring secure communication, especially in scenarios where sensitive information is being transmitted, such as using Wi-Fi in public places.

The other options don't accurately represent a VPN. A physical security device relates to hardware that protects against unauthorized access to physical premises or equipment. A web application firewall is a specific cybersecurity tool designed to monitor and filter HTTP traffic to and from a web application, focusing on preventing attacks like SQL injection or cross-site scripting. Unauthorized access methods refer to illicit techniques used to gain entry into a network or system without proper permission, which is contrary to the legitimate use of VPNs that provide secure access rather than unauthorized access.