Communication between client and DeleGate or between DeleGate and server
can be filtered or translated by user defined
programs attached to DeleGate using a simple scheme named
CFI (Common Filter Interface).
Existing filter programs, from standard input to standard output,
can be used as a CFI program without modification.
Besides filtering by external programs,
some of frequently used filtering operations are built-in to DeleGate,
including HTTP header removal