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
killers 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.