Matt Brown <[EMAIL PROTECTED]> writes:
> This has been a feature of recent spam, which is probably why it's now
> an issue. Several spam senders are now having sender addresses of
> <spammer>@<spamdomain>, where <spamdomain> resolves via DNS to
> '0.0.0.0'.
>
> Eventually qmail rejects the message because it recognises that it's
> looped around too much, of course.
Right, but it's a very effective (perhaps inadvertant) DOS tool. If
you can generate a stream of 10 messages/sec of these, it's the
equivalent of generating about 300 messages/sec --- a great way of
turning a puny dial-up connection into a mail server crushing machine.
We had a spammer sending a huge number of messages to users at this
address (<sigh> their fake bounce addresses are now getting on each
others' list...), which was causing our not-processed queues to hover
around 100, which was causing regular messages to be processed very
slowly.
Since qmail works around this simple mail loop for other address
referring to the local machine, it should do so for 0.0.0.0 as well.
------ScottG.
