S/MIME usage: data that has been signed with a digital signature, and then encrypted, and then signed again.
A computer program that appears to have a useful function, but also has a hidden and potentially malicious function that evades security mechanisms, sometimes by exploiting legitimate authorizations of a system entity that invokes the program.
Trunking is connecting switched together so that they can share VLAN information between them.
Trust determine which permissions and what actions other systems or users can perform on remote machines.
Trusted ports are ports below number 1024 usually allowed to be opened by the root user.
A communication channel created in a computer network by encapsulating a communication protocol's data packets in (on top of) a second protocol that normally would be carried above, or at the same layer as, the first one. Most often, a tunnel is a logical point-to-point link - i.e., an OSI layer 2 connection - created by encapsulating the layer 2 protocol in a transport protocol (such as TCP), in a network or inter-network layer protocol (such as IP), or in another link layer protocol. Tunneling can move data between computers that use a protocol not supported by the network connecting them.