A system and method for adaptively verifying data in resource constrain systems. The adaptive data verification mechanism employs the proper mode of verification adaptively to balance cost/performance requirements plus security requirements. The algorithm uses a belief level for the validity of a received message, and assigns the belief level to a scale between a bona fide message at one end of the scale and a malicious message at an opposite end of the scale. Depending where on the scale the belief level falls determines which validation mode will be used to authenticate the message. In an alternate embodiment, the belief level relative to a scale and the amount of data waiting to be processed in a buffer are both used to determine which mode will be used to validate the message.