A system and method for protecting components of an IP telephony network whereby a protection scheme is enabled upon detection of resource exhaustion within the network that prevents delivery of incoming messages. Resource exhaustion may result from denial of service attacks and/or malfunctions in automated dialing systems. Once a protection scheme is enabled, the system activates mechanisms for identifying calling parties that are suspected of contributing to the resource exhaustion condition. These suspected calling parties may be placed in a blocked sender list, either manually or automatically. Calling parties may be presented with a challenge function in order to determine whether the call is being made by an automated dialing system. The system blocks incoming calls from calling parties identified in the blocked sender list either permanently or for a specified time duration. The protection scheme remains enabled for a specified duration or until the resource exhaustion condition has subsided.