[Hikikomori]

Just to clarify, it was a small Nigerian ISP that caused this, CT just propagated it to others. It's likely that this Nigerian ISP was setting up peering with Google and misconfigured their route policy. If you do this incorrectly you can advertise prefixes you get from one peer to other peers as if you own it. (essentially you replace the full AS path (prefix metadata in BGP) with your own AS number, it makes it looks like you originated the prefix to others) If neither the Nigerian ISP or CT refused to do anything then everyone that is their peer or customer would need to manually filter this "bad" prefix" to stop it. Customers and ISPs that only use CT would still be affected.