Received SIP subscribe for peer without mailbox:XXX

I am receiving too many messages like “Received SIP subscribe for peer without mailbox: XXX”, where XXX is a random number on each attempt.
Is it possible that my Asterisk is undergoing an attack ?
Am I receiving attempts to random peer connections ?

Thanks.

No, your sip client(maybe xlite,bria) sends the subscribe without mailbox.

That is just SIP Methods Used by a SIP Phone to establish a SIP dialog for receiving statistics. A typical example is MWI information for the phone’s configured Extension Number.

Thank you for the answers.