How exactly proxy is supposed to behave
when it "hangs onto" say 10.000 + unfinished
TCP connections ? Will it deny new ones (because
resources are always limited) ?
Looks like it's the only thing it will be able
to do and as soon as first packet is denied,
hacker's won.
As hard as it is to be implemented the only way
to fight this is have every single ISP to filter
outgoing packets.
Assuming big players have enough desire they can do it
quickly by making an offer smaller ISPs can't refuse,
the same kind Sprint made when it started filtering
small CIDRs.
It's certainly harder to catch those who don't comply
though ...
Interestingly enough, the source IP's could be valid,
then it becomes even harder to see if the TCP connection
request is valid or bogus. And once again, source filtering
by ea and every AS looks like the only solution.