[DCC] Re: whitelist trouble

Kelsey Cummings kgc@corp.sonic.net
Mon Apr 16 18:51:44 UTC 2007


On Mon, Apr 16, 2007 at 09:56:12AM -0600, Vernon Schryver wrote:
> >                                                          That way,
> > completely empty messages could be given special treatment.
> 
> The trouble is that the messages are not completely empty but contain
> a little text that the recipient presumably wants to see or is to be
> forced to be seen by free mail providers and other advertisers.   After
> you ignore random looking strings of digits and letters and other
> cybercrud from a return receipt, each is identical to all others and
> so has the same checksum.  Nominally empty messages from free mail
> providers have advertising crud that is the same as zillions of other copies.

Or in some cases don't appear to be empty at all.  They have a typical
message body, for example, along with the 'This message certified virus
free by AVG Version 1.2.3.4 definitions 5.6.7.8' attachment which
occasionally hits thresholds and causes rejections.

> > Otherwise, we would need some automated procedure to detect these
> > messages and whitelist them by their conventional checksums.
> 
> There is John Levine's semi-automatic list of checksums of empty
> messages.  The script /var/dcc/libexec/fetch-testmsg-whitelist
> can be run from cron to fetch 
> http://www.iecc.com/dcc-testmsg-whitelist.txt
> and/or other lists.

That certainly helps, but it seems like I've been adding a couple a month
for a while now.  I'm not sure if this is a change in DCC or regular
changes in Outlook/OE and AVG.

This is just one of those things that it would be great if DCC could be
made to handle which would allow me to continue to use the included milter
hooks.  Otherwise I've got to move it over into something like Mimedefang
and selectively deliver to and or pre-process mail before delivery to
dccd/dccproc which is okay but doesn't address it as a general complaint on
an otherwise wonderful tool.

It's really just these two specific cases too.  AVG signatures and
Outlook/OE read receipts, nothing else causes any trouble.

-- 
Kelsey Cummings - kgc@corp.sonic.net      sonic.net, inc.
System Architect                          2260 Apollo Way
707.522.1000                              Santa Rosa, CA 95407



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