A bit stumped by this. Alblasco can you help me out?
I launched the asterisk console (asterisk -r) and was barraged with multiple instances of this message:
[Nov 24 20:10:38] NOTICE[3002]: chan_sip.c:24905 handle_request_register: Registration from '"3551" <sip:3551@MYIP-censored>' failed for '195.154.32.252:5763' - No matching peer found
195.154.32.252 comes up in google as a known malicious IP
I used to have SIP ports open to external but as a result of this disabled them. The attack is still somehow getting through.
I managed to block the attack using
iptables -A BLOCKLIST -s 195.154.32.252 -j DROP