VPNs have become something of a religious icon for the networked user who is concerned about the secure transmission of sensitive data. Where private networks once consisted of secured leased lines that were access-protected by a unique user name and a password, VPNs generally operate over a known non-secure network.

VPNs encrypt data transmitted from an access point before it hits the network, and decrypt all received traffic before it gets to the user. This basic functionality, not the medium the VPN spans, is the true definition of a VPN. The rest is merely details of implementation.