A technique that reduces the possibility that a message received at a computer terminal during an instant messaging conversation will become accessible to unintended viewers. One embodiment is directed to an arrangement wherein a computer terminal at a first client work station is disposed to receive chat messages from a second client work station during an instant messaging conversation. An apparatus associated with the computer terminal for limiting access to the received chat messages includes a device for attaching a security identifier to each received chat message. A display device at the computer terminal generates a window that selectively provides a specified one of the chat messages in viewable form. A concealment device coupled to the display device is operable to make the specified chat message unviewable on the display device. A component connected to the concealment device activates the concealment device when a prespecified event occurs.