[Mailman-Users] Removing attachment
Brad Knowles
brad at stop.mail-abuse.org
Tue Feb 22 23:01:02 CET 2005
At 1:43 PM -0800 2005-02-22, Allen Watson wrote:
> It really would be so much better if there were a simple setting to
> reject ALL messages with attachments, as some other mailing list
> software provides. It can't be so difficult...
Actually, yes it is. MIME bodypart types come in pairs, and
there are an unlimited number of potential combinations of these
pairs. Moreover, there are also a variety of other
attachment/encoding techniques (uuencode, binhex, etc...) which do
not depend on MIME at all, and in fact would look to the program just
like normal ASCII text. Indeed, the entire purpose of many of these
alternative encoding techniques was to be able to survive being
transmitted via 7-bit ASCII-only transmission networks, such as can
be provided by e-mail.
And don't get me started on steganography.
Given that there are an unlimited number of possible encoding
techniques, it is physically impossible to block them all.
This is why Mailman provides the tools that it does, and it
allows you to choose to either filter out the stuff you know to be
bad (allowing through everything else), or to allow through only the
stuff you know to be good (filtering everything else).
This problem is much more complex than you give it credit for.
Do Internet e-mail systems administration for a decade or two, and
you'll find that there are all sorts of bizarre things out there that
you never thought could possibly exist.
Mailman can only deal with those things that it knows about, and
we've given you powerful tools that will help you solve most of the
problems, if you use them correctly.
--
Brad Knowles, <brad at stop.mail-abuse.org>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
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