https;\\raw[dot]githubusercontent[dot]com/ipverse/asn-ip/master/as/213035/ipv4-aggregated.txt and
https;\\raw[dot]githubusercontent[dot]com/ipverse/asn-ip/master/as/213035/ipv6-aggregated.txt
where 213035 is the ASN of Serverion BV, will return the list of IPv4 and IPv6 subnets. I have scripts using ipverse data to block entire providers in the firewall on a regular basis.
You can find ASNs by doing a whois on the IP address currentl attempting spamming/port scanning/phishing/hacking.