>>>>> "Jonathan" == Jonathan Stone <jonathan@DSG.Stanford.EDU> writes:

    >> Not every site filters incoming traffic. Sad but true. Security
    >> systems should be robust in depth.

    Jonathan> So that's a reason to exclude another defense method???

So. It's a reason not to build a security mechanism on top of some
other mechanism - like "all IP packets have truthful addresses" -
which is patently false.