/d[y]oop loop/ (also "dupe loop") [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.

[Jargon File]