VPN

UNIT had a VPN tunnel in the early 21st century, which Osgood used to "ping IPs", in an attempt to regain access to the Internet in John Benton's pub, the White Hart. (AUDIO: Call to Arms)

Behind the scenes
IPVanish, a real world VPN, briefly appeared in WC: The Zygon Isolation, although it was not named or described in the webcast outside of its logo appearing.