It is based on how a service provider (like Netflix) classifies an individual or block of public IP addresses.
One of they ways they do this is by ASIN numbers to figure out who owns what IP addresses and what they are been used for.
Also, If you do a quick google of “AWS IP Address Blocks”, the first result is how to view AWS current IP Address ranges - AWS IP address ranges - Amazon Virtual Private Cloud
This would make it very easy for Netflix to keep an up to date database of IP addresses to block.
Netflix might also block an IP address if they see unusual activity originating from that IP address.