callback

callback
    n 1: a request by the manufacturer of a defective product to
         return the product (as for replacement or repair) [syn:
         {recall}, {callback}]
    

call-back \call-back\ n.
   1. a return call, especially a telephone call.
      [WordNet 1.5]

   2. the recall of an employee to work after a layoff.
      [WordNet 1.5]
    

callback

   1. <programming> A scheme used in {event-driven} programs
   where the program registers a {subroutine} (a "callback
   handler") to handle a certain {event}.  The program does not
   call the handler directly but when the event occurs, the
   {run-time system} calls the handler, usually passing it
   arguments to describe the event.

   2. <communications, security> A {user authentication} scheme
   used by some computers running {dial-up} services.  The user
   dials in to the computer and gives his {user name} and
   {password}.  The computer then hangs up the connection and
   uses an {auto-dial} {modem} to call back to the user's
   registered telephone number.  Thus, if an unauthorised person
   discovers a user's password, the callback will go, not to him,
   but to the owner of that login who will then know that his
   account is under attack.

   However, some {PABXs} can be fooled into thinking that the
   caller has hung up by sending them a dial tone.  When the
   computer tries to call out on the same line it is not actually
   dialing through to the authorised user but is still connected
   to the original caller.

   3. <communications> {cost control callback}.

   (2003-07-13)