Methods and apparatus for controlling the operation of a distributed application using message interception techniques are disclosed. The message interception software is independent of the software components making up the distributed application. The message interception software processes messages by carrying out a series of actions set out in an interceptor chain configuration policy, that policy being selected on the basis of the contents of the intercepted message. The interceptor chain configuration policy is divided into a separate enforcement configuration policy which dictates what actions should be carried out on a message and in what order, and an interceptor reference policy which indicates references to interceptors which are suitable for carrying out the actions specified in the enforcement configuration policy. In this way, the behavior of the message interception software (and thus the distributed application) can be updated while both the interception software and the distributed application are running without requiring the person updating the behavior of the message interception software to deal with esoteric references to interceptor software routines.