Perhaps fail2ban will work, but add
alwaysauthreject=yes
somewhere in your sip.conf hierarchy for completeness.
Althought these guys are a PITA, don't underestimate them, they are NOT stupid, (ask google, they got screwed) I suggest you ban the entire networks at /8 on your firewall, ok, so some folks in china and japan won't be able to register with you but is that a problem? look into csf as a a firewall and it's ability to do bans by ipcountry, most of this crap comes from China closely followed by eastern Europe, go figure
dicko
(
yum -y install jwhois
whois 119.147.116.0
etc.
)