BCP38 thread 93,871,738,435

Thu Oct 26 15:07:32 UTC 2006

* Steven M. Bellovin:

> As you note, the 20-25% figure (of addresses) has been pretty constant
> for quite a while.  Assuming that subverted machines are uniformly
> distributed (a big assumption)

I doubt this assumption about distribution is valid.  At least over
here, consumer-grade ISPs (think DSL with dynamic IP addresses) apply
ingress filters, while real ISPs don't.  If you're lucky, you get
egress filters at some border routers, but it's not standard at all.
Customer-facing interfaces are generally unfiltered.

(But I have to admit that we recently ran into filters at an
upstream's upstream, so there's at least some BCP 38 adoption.)