Signal detection and blocking for voice processing equipment

A method of processing a telephone call comprising voice signals and data signals between a caller and an agent, the method comprising: receiving a trigger signal indicating that sensitive information is about to be received from the caller; receiving from the caller at a first telephone interface data signals comprising sensitive information; and in response to having received the trigger signal, masking at least some of the data signals to prevent at least some of the sensitive information from being transmitted via a second telephone interface to the agent. Preferably, voice communication between caller and agent is maintained. Corresponding apparatus is also disclosed.