During tunneling, data from one protocol is embedded in another network protocol. This allows for secure (encrypted) connections (such as SSH) to be created via unsecured networks (TCP/IP, SMTP). A tunnel can also be used to circumvent a firewall. A user from the intranet can employ an outgoing tunnel to access external computers, networks or services. An incoming tunnel allows an external user access to a service, computer or data on the intranet.