Do hiring policies usually forbid hiring someone who's committed a felony, ever, or just within the past x number of years?

I was always under the impression that when employers refuse to hire felons, they mean any felony, ever. You can be a 55 year old who bounced a check 30 years ago and be just as ineligible for that job as someone that murdered their spouse 3 years ago. But upon reading this “Must be able to pass FBI Background Check to obtain Security Clearance (i.e. No Felonies in past five years)”, I’m suddenly questioning that. Is 5 years more the standard?