A method and apparatus are disclosed for establishing a field deployable message compromiser which is connected between two network elements and identifies and removes predetermined messages from an incoming message stream. Subsequent to removal the test protocol processor may perform one or more of several actions according to the results of statistical calculations. These actions include allowing the message to drop, replacing the message after a delay, replacing the message after altering the payload of the message, and replacing the message after altering the message type. The disclosed field deployable message compromiser is particularly useful for providing a means to perform in situ field testing of network performance indicators under desired statistical conditions.