But it costs space in the routing tables and that means replacing routers earlier. It's no wonder, especially if you multiply it by thousand customers.
"block all traffic from outside from this IP" is significantly easier than "block all traffic from outside from this IP to this client". And you need to do it per ISP client, else it is ripe for abuse.
And don't forget a lot of the traffic will come from "cloud" itself.
But you should own an AS for that?
> But it costs space in the routing tables
Not implementing my proposal leaves critical infrastructure unprotected from foreign attacks. Make larger routing tables. Also, instead of blocking single IPs one can block /8 or /16 subnets.
Brilliant! Why didn’t we think of that?!? MOARE TCAMS!!!
Also, in Russia for example, there is DPI inspection and recording of all Internet traffic and if it is possible in Russia, then West can probably do 10x more. Simply adding a blacklist on routers seems like an easy task compared to DPI inspection.