A file maintained to show one's innocence after an anticipated disaster takes place. (After the attempts to avoid blame for the failure to prepare to defend the U.S. Naval Base at Pearl Harbor, Hawaii from Japanese attack.)

Also a generic name for any file maintained in order to minimize damage after an  anticipated bad result for actions taken against one's better judgement or under duress. --RaySchneider

Compare with SixtyMinutesFile. See also WatchYourSix.