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SpamDunk procmail filter March 26, 1999 update

1999-03-27 00:17:59
  The most recent update is March 26/1999. People with recent
versions of SpamDunk need only download
http://www.interlog.com/~waltdnes/spamdunk/sdfiles/NOTLIST.TXT
and upload as "isnotlist".  Reasons for update...
 - Hopefully my last major bug for Exim email squashed, i.e.
   false-positives for the open-relay-hijcking filter. My
   apologies for the problem. When I wrote the first, sendmail-only,
   version of SpamDunk, I had it on my account for a few weeks with
   daily tweaking before even the beta version went public. I did
   not have this luxury when my ISP cut over to Exim as a replacement
   for Sendmail. I will continue to keep SpamDunk compatable with
   sendmail, because 
   a) I want my filters to work for as many people as possible 
   b) I still have to deal with email from sendmail-using sites
      even though my ISP uses Exim.

 - False positive open-relay-hijcking flagging of Hotmail email
   fixed. This required special handling for one non-standard
   header that Hotmail puts out.

 - In my previous update, I included a filter to reject email from
   SMI-8.6. It was brought to my attention that there are good
   internet citizens out there who do go to the effort of setting up
   a non-relaying firewall machine in front of the SMI-8.6 machine.
   To avoid punishing them I've tweaked my filter to only flag email
   where the SMI-8.6 header occurs on the first header physically
   below (i.e. chronologically before) the handoff from the external
   system to your ISP's server. If there is an intervening header
   from another machine in the sender's system, it's considered to
   be a firewall. 

--------------------------------------------------------------------
Known issues that can't be resolved, due to the nature of SpamDunk. 
--------------------------------------------------------------------

 - The open-relay-hijacking filter can't tell the difference between
   authorized and unauthorized 3rd-party relaying. Workarounds are...
   a) Whitelist trusted correspondents, who use relays, in the
     "procvars" file, or 
   b) Delete or comment out lines 102 through 125 in "NOTLIST.TXT"
      before uploading it as "isnotlist". WARNING, this will eliminate
      all checking for open-relay-hijacking. 

 - Certain Microsoft mail clients generate their own weird
   "Message Id:" headers that throw SpamDunk for a loop, generating
   false positives all over the place. They're the only people who do
   this. But of course, they're the same outfit who's email clients
   default to sending out HTML, RFT, or MS-Word files instead of
   regular ascii text.  MS doesn't seem to have a clue about standard
   internet practices. Workarounds are... 
   a) Whitelist trusted correspondents, who use the offending MS
      products, in the "procvars" file, or 
   b) Delete or comment out lines 52 through 167 in "NOTLIST.TXT"
      before uploading it as "isnotlist". *WARNING*, this will
      eliminate all checking for 
      - invalid "Message Id:" headers. This test catches a lot of
        spamware output.
      - email with no "Message Id:" headers generated by the sending
        system, where your ISP's mailserver will probably insert its
        own header. This test also catches a lot of spamware output,
        especially RFMS spew.
      - open-relay-hijacking in general
      - Your ISP receiving email direct from an insecure SMI-8.6
        mailserver 
      - email with forged "From:" headers claiming to be from
        commonly-forged domains like earthlink, freeyellow, juno,
        hotmail, wowmail, yahoo, not to mention others that you can
        add manually. 

-- 
Walter Dnes <waltdnes(_at_)interlog(_dot_)com> procmail spamfilter
http://www.interlog.com/~waltdnes/spamdunk/spamdunk.htm
Why a fiscal conservative opposes Toronto 2008 OWE-lympics
http://www.interlog.com/~waltdnes/owe-lympics/owe-lympics.htm

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