1. A method for authenticating messages received at a receiver, said method comprising: establishing a belief level for senders of messages that are received at the receiver as to the messages validity; assigning the belief level to a scale where one end of the scale indicates a bona fide sender or message that will be accepted and the other end of the scale indicates a malicious message or sender that will be discarded; selecting an authentication mode based at least in part on the belief level, wherein one authentication mode includes a blind accept mode for a belief level at or around the bona fide end of the scale, a discard mode for a belief level at or around the malicious end of the scale and at least one mode therebetween; and performing an authentication process on the message depending on which mode is selected.