Intelligence source and information reliability rating systems are used in intelligence analysis.
A system commonly employed rates the reliability of the source as well as the information. The source reliability is rated between A (history of complete reliability) to E (history of invalid information), with F for source without sufficient history to establish reliability level. The information content is rated between 1 (confirmed) to 5 (improbable), with 6 for information whose reliability can not be evaluated.
For example, a confirmed information from a reliable source has rating A1, an unknown-validity information from a new source without reputation is rated F6, an inconsistent illogical information from a known liar is E5, a confirmed information from a moderately doubtful source is C1.
The evaluation matrix as described in the Field Manual FM 2-22.3 (see also Admiralty code):