The IFF system of the Stinger weapon system is surprisingly robust, and non-trivial to circumvent. It essentially prevents you from locking on to any vehicle equipped with an IFF transmitter (meaning if you point a western-made Stinger at a western commercial aircraft, it won't let you fire at it). As such, I doubt there will be any significant impact from "unsecured" Stinger systems floating around, though that does not negate similar consequences from non-IFF-equipped weapon systems.