As much as you don’t need to know I think you should know. This has to deal with “local” vs “remote” ports. Yealinks are especially vulnerable to this because their local ports start at 5060. While other manufacturers local ports are random. What happens in the case of Yealinks (and grandstreams) is that they “poke” a hole in your firewall so that the remote server (asterisk, freeswitch, etc) can “hit” that port, when they use 5060 they are using the commonly known port that all SIP uses so it’s easy for a sipvicious attack to just ring your phone all the time. I’ve had this happen several times, the best thing to do is just go into the phone’s interface and change the “local” port. Everyone should do that anyways.