It may have been due to an ASN belonging to Level3. You can read about this here
. The CloudFlare write up is especially informative. Pretty damn incredible if you ask me. Probably should do what CloudFlare does and get rid of the use of Flowspec if that is the source of the issue. The fact this affected techs to even access the router/s is crazy.
If this is all too complicated to understand, then this is what happened in a nutshell. https://www.youtube.com/watch?v=zAJbOygaJ0o