HI.
From: "David F. Skoll"
Subject: [Mimedefang] Strange activity
Has anyone noticed some strange activity lately? Specifically, one of our
customers has been hit by hundreds or thousands of machines that open SMTP
connections to his boxes and then just sit there, leaving the connection
idle. This wreaks havoc by creating tons and tons of Sendmail processes.
I would like to suggest another possible explanasion to the "buggy" spam bot.
Issues like that might also be related to MTU .
Have you checked the MTU value of your customer mail servers?
Can you try to ping with different packet sizes to some of the sender IP
addresses?
I do agree that the most reasonable explanasion so far is a
spam/dictioanry/other attack software,
but in addition you should also consieder layer 3 networking issues,
or a combination of attacks hanging due to layer 3 problems or client side limitted bandwidth.
Yizhar Hurwitz
http://yizhar.mvps.org
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