The invention contains an application operating environment in which acceptable and/or suspect activities may be defined for an application so that unacceptable application behavior can be prevented. This is done by providing a definition table identifying the types of access and actions that the application is allowed and preventing it from carrying out other types of access and actions. The definition table may be built up using a learning process during use of the application. The environment also provides a means of checking information output to a network against a list of confidential information.