It's useless... IP addresses are easily spoofed and in fact usually are, in a botnet. When they're not spoofed it is legitimate service providers that through no fault of their own, happen to have some customers with zombie computers in the botnet. You'll wind up blocking legitimate people - the exact defeat of this addon.
You have no way of knowing if that IP is spoofed. You can block it then have the exact crap coming right back with a different IP.