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The purpose of the Intrusion Detection Message Exchange Format (IDMEF) is to define data formats and exchange procedures for sharing information of interest to intrusion detection and response systems and to the management systems that may need to interact with them.

As for today, the IDMEF RFC specifies two major classes of objects:
An alert can be send:
Hearbeats are generaly sent by all analyzers to inform Managers that they are correctly running.