Yes, but egress filtering is only effective by far. Anyone can forge the source to an IP address that belongs to one of the /16's a provider advertises.Good point.
I suppose another basic but effective method of prevention would be egress filtering. An increasing minority of network providers are instituting it, but it doesn't seem like it will be a widespread thing in the near-term.
It will help of course, but really not The solution... Or is there one?
-hc
