There is some misinformation in previous posts that I would like to
clarify on the Level 3 side of things.
Every transit-like connection on AS3356 is prefix-filtered including all
parties in this event. On AS3356 all prefix filters and import policies
on BGP sessions are audited and checked in almost realtime for people or
system errors (missing, mis-referenced, not referenced, otherwise broken
config, etc.) The prefix filters themselves are generated using data from
Level 3's own registry and known public route registries. As several
folks have pointed out there are minimal checks for the validity of the
source information.
Further details on Level 3 filtering policies are available at:
whois -h rr.level3.net AS3356 | grep remarks
As an aside I see an increase in the number of downstreams asking for
as-path filtering or *no* filtering usually with justifications of ISP X
doesn't require us to register routes or just does as-path filtering. In
my opinion that is bad news for everyone as documented in numerous
BCPs, presentations and route-leaks.
-Kevin
Disclaimer - I do work for Level 3 but am expressing my opinions and not
those of my employer.
