When processing messages, why would the software put trust in information from data soure(s) that were credible up till now? It seems easy to be fooled by a wel

When processing messages, why would the software put trust in information from data soure(s) that were credible up till now? It seems easy to be fooled by a well-informed source that keeps posting accurate information from beginning right until the `trap' (police kettle) springs -- and kelping the kettle by posting a false piece of information at the right time. Kettle planers would have both means and incentives in doing just that.