dup loop

dup loop /d[y]oop loop/ (also `dupe loop') n.  [FidoNet]
   An infinite stream of duplicated, near-identical messages on a
   FidoNet {echo}, the only difference being unique or mangled
   identification information applied by a faulty or incorrectly
   configured system or network gateway, thus rendering {dup
   killer}s ineffective.  If such a duplicate message eventually
   reaches a system through which it has already passed (with the
   original identification information), all systems passed on the way
   back to that system are said to be involved in a {dup loop}.