VPN (Virtual Private Network) is a generalized name for technologies that allow one or more network connections to be provided over another network. Despite the fact that networks with a lower or unknown level of trust are used for communication (for example, public networks), the level of trust in the constructed logical network does not depend on the level of trust in the underlying networks due to the use of cryptographic tools (encryption, authentication, public key infrastructure, tools protection against repetitions and changes in messages transmitted over the logical network).

Depending on the protocols used and the purpose of VPN, it can provide three types of connections: node-to-node, node-to-network and network-to-network.