I believe this was alo used by hackers/crackers back in the modem era. When you connected to a corporate system the system would first identify you, then drop t

I believe this was alo used by hackers/crackers back in the modem era. When you connected to a corporate system the system would first identify you, then drop the connection and call you back to your official number. If you did not hang up, the system ended up connecting back to you.