You're better off using a combination of IP blocklisting and ratelimiting, both of which use some sort of binary tree to speed up lookups, rather than using a m

You're better off using a combination of IP blocklisting and ratelimiting, both of which use some sort of binary tree to speed up lookups, rather than using a mega-regex which your solution proposes, which, with tons of backtracking, is very likely slower than serving the request would have been. Not to mention that user agents are easily spoofable.