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.
--
Steve.
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