Steve Phillips wrote:
Jessica Zhu wrote:
Hi Ed,
On Tue, 23 Aug 2005, Ed Wilts wrote:
On Tue, Aug 23, 2005 at 10:09:02PM +0600, Aroop Maliakkal wrote:
The <> messages are bounced messages. Someone may be spammed from
your server and those address falied is bouncing back now. Make
sure your server is secure and no one abusing it. Check for
malicious scripts ...( expecially in /tmp..)...
Have a nice hunting:-)
/tmp was checked. Nothing turned out. Part of the bounced back
messages which included detailed header for original mail checked,
till now no one is really from us.
Another possibility is that somebody outside of your organization
forged
their From: addresses to be from your domain. They then spam like
crazy
and all the bounce messages go to you. Somebody did that to us and
it's
not easy to recover from. The bounce messages come from all over so
you
can't block the senders (the sending host is likely legitimate anyway).
That's exactly what happened to us. Somebody outside of our
organization forged the From: addresses and we became the victim to
that. At this point, it seemed that our syslog is so busy to write
the maillog that it becomes a heavy process. This morning around 8AM,
this drives our system load over 20 and the system becomes slower and
slower. Now it seemed the worst time is over. However, I worried with
such baounced back volumes increasing, our system can not afford to
it finally.
In our case, it happened to be a inactive domain. We just directed
that
domain to a black hole and the firewalls dropped the smtp messages. If
the domain is active, there's not a lot you can do except ride out the
storm. Are the messages coming to random usernames or a handful of
specific ones? If they're specific, you can add mail access rules to
All the messages come to random usernames. A lot don't exist.
sendmail to discard those and that will help the flood a bit. If
they're random, you can't block by source and you can't block by
destination. Not good...
No penalty is severe enough for a spammer.
Absolutely. We cannot afford the system down. So really hope someone
here has the solution for this.
Jessica
Jessica Zhu wrote:
Hi,
It looks like we are experiencing the mail attack now.
In our maillog, we have a lot of User Unknown message like the
following.
Aug 23 11:52:25 s1 sendmail[2110]: j7NFqPL02110:
<Oscard@xxxxxxxxxxxxx>... User unknown
Aug 23 11:52:25 s1 sendmail[2110]: j7NFqPL02110: from=<>,
size=17601, class=0, nrcpts=0, proto=ESMTP, daemon=MTA,
relay=mail.vis-inc.net [66.77.28.202]
It looks like that all the from is <>, does anyone have the way to
fight against it.
Jessica
in syslog.conf add a - to the start of the filename like so
mail.*<tab><tab><tab>-/var/log/maillog
The - tells syslog not to do an fsync each message and _really_
reduces syslog load when it is busy, this will probably bring your
mail server under a little more control.
The next thing to do is examine the bounce messages and find out where
this originated and ring them. If this is still ongoing and they have
not terminated the spammer then add a postmaster redirect for that
domain temporarily to the postmaster@xxxxxxxxxxxxxxxxxxxx and you will
find the problem gets fixed usually within hours.
This happened to me with an AOL user spamming using <random
characters>@internet.co.nz and i was getting a few thousand messages
an hour comming into my postmaster account, after being told by a
monkey to "forward the spam to postmaster@xxxxxxx sir !" and refusing
to discuss the issue I forwarded the 50,000 odd boounces I had
collected and added a redirect and within about a day it had stopped.
The big trick is to find the originator. - If you need help with this
them let us know and we can probably track them down for you.
Another option is (Just a thought) :- to Null route the mx record of
the domain to which bounce is coming....if it is possible give low ttl
value....It will take some time to get the result in effect because mx
will be cached by most of isps.
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