Voici quelques logs :

159.223.5.5 - - [03/Nov/2021:13:00:43 +0100] "GET /3000D00E0000FFFF3F0031313744373731343634304537353046007A7A7A7A7A7A7A7A7A7A7A7A7A7A7A0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001000008047A7A7A7A7A7A7A7A7A0000000000000000000000000000000000000000000000000000000000000000 HTTP/1.1" 403 443 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 1.1.4322)"
159.223.5.5 - - [03/Nov/2021:13:00:46 +0100] "\xbf\xbf\xaf\xaf~" 400 0 "-" "-"
159.223.5.5 - - [03/Nov/2021:13:00:46 +0100] "POST / HTTP/1.1" 302 256 "-" "WinHttpClient"
159.223.5.5 - - [03/Nov/2021:13:00:48 +0100] "\x17\x03\x01\x01\x04e" 400 0 "-" "-"
159.223.5.5 - - [03/Nov/2021:13:00:48 +0100] "\x17\x03\x01\x01\x04e" 400 0 "-" "-"

Comme toujours c’est DigitalOcean :

IP Address	Country	Region	City
159.223.5.5	Netherlands	Noord-Holland	Amsterdam
ISP	Organization	Latitude	Longitude
DigitalOcean LLC	Not Available	52.3740	4.8897

Bye-Bye :

iptables -A INPUT -s 159.223.5.5 -j DROP