Abbreviation for "Virtual Private Network". In the course of the Internet boom, virtual private networks found solid footing in the infrastructure of corporate networks. A (company's) internal data transmission is performed over an existing public network; the data packages are encrypted for transmission. The key pairs are only known to the sender and the recipient. The encrypted data packages are normally packed in TCP/IP packages. This procedure is called “TCP/IP tunnelling”. This also permits the transmission of NetBIOS or IPX data packages over the Internet. See also: Remote data transmission (RDT), Encryption, TCP/IP.