DCC -- how do I effectively use it?

Mediratta, Bharat bharat@fusionone.com
Mon Sep 3 09:15:09 UTC 2001

> From: Vernon Schryver [mailto:vjs@calcite.rhyolite.com]
> However, you'd be better served with your own DCC server exchanging
> "floods" of checksums with other DCC server servers.  Besides being
> more robust, faster, and using even less bandwidth, with your 
> own server you could look at your copy of the database of checksums 
> with dblist.

I'm definitely heading in that direction.  In fact I'll contact
you privately to get an id and password.

> Other people with access to the same checksums have seem to have
> had better luck.  However, I think 25% is nothing to sneeze at.

Absolutely.  And it will only get better with time.  I just wanted
to make sure that I wasn't pointing at the wrong database.

>   - bugs in the IMAP client code might be changing the messages so
>    that their checksums don't match.  

Entirely possible.  I'm using Net::IMAP on top of cclient-0106191041
on FreeBSD 4.3.  My code assembles the message by combining the
raw rfc822.header and rfc822.text values and passes it to dccproc.

>   - I'm still fighting hassles with quoted-printable and making
>    dccproc get the same checksums as dccm.  One often sees messages
>    converted from convereted from quoted-printable and with CRLF
>    converted to CR while the other doesn't.

If I can help track this down, let me know.  
>   - as part of those hassles, I've changed the fuz1 checksum in
>    version 1.0.28 to not ignore the last line.  Until everyone starts
>    using that code, the effectiveness of the fuz1 checksum 
> will be reduced.

Where can I get 1.0.28?

>   - the spammers who like you differ from those who like DCC users
>   - your name is early in the typical spammer's somewhat alphabetical
>    lists 
>   - you are rejecting only on "many" instead of a threshold approprate
>    for the number of your local users.  (Yes, that wouldn't apply to
>    checksums with counts of 1.)

Right now my simplistic algorithm says that it's maybe spam if any of
Message-ID, Received, Body or Fuz1 are greater than 10.  Definitely 
spam if it's greater than 50 (or "many").  But yeah, mostly the problem
is that the messages haven't been seen before.

> ] Will you also support a mode of operation where the MTA has already
> ] "dcc"ed the message and put it's (DCC's) header in the 
> message?  i.e.
> ] simply parse the IMAP INBOX for messages with existing DCC headers
> ] with values of n>1 where n is some configurable values (rather than
> ] using dccproc on the messages)?

I figure that if the MTA has dcc'd the message (or spambounced it or
used some other spam detection code), the mail client/server can do 
filtering as appropriate.  My script is purely to glue DCC together 
with a system that has no inherent spam detection.

By the way, y'all rock.  It's nice to work with professionals.

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