Source : Free On-Line Dictionary of Computing

iron box
     
        [Unix/Internet] A special environment set up to trap a
        {cracker} logging in over remote connections long enough to be
        traced.  May include a modified {shell} restricting the
        cracker's movements in unobvious ways, and "bait" files
        designed to keep him interested and logged on.  See also {back
        door}, {firewall machine}, {Venus flytrap}, and Clifford
        Stoll's account in "{The Cuckoo's Egg}" of how he made and
        used one.  Compare {padded cell}.
     
        [{Jargon File}]