backscatter joe-job attack

[Bob Proulx]

FYI: I routed a nonexisting address to /dev/nullon on debbugs tonight
to mitigate a backscatter joe-job style attack to it.  Some dozens of
outlook.com exit nodes are connecting and dumping what looks like
backscatter to an 11 digit number address.  WAT?  I have no idea.  But
it is consuming so many parallel TCP SMTP connections that valid
connections are receiving "421 Too many concurrent SMTP connections; pleas\
e try again later." status returns which is delaying legitimate
connections.

I am hoping that things eventually drain and stop.  That's all I know.

Bob