This refers to Sip vicious, call scanner , phone ringing all night
“Friendly scanner” isn’t an attack type, but rather what the FreePBX dialplan reports when a call arrives for an unknown DID. Where the cause of this is malicious, one can normally stop it by not enabling anonymous callers. With chan_pjsip, there should not really need to be any reason to enable these, although with chan_sip, it was sometimes necessary when a provider could originate traffic from a range of addresses. chan_pjsip, allows you to specify a list of addresses and address ranges for an endpoint.