作者 主題: [問題]關於SPAM  (閱讀 1529 次)

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yufeng

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[問題]關於SPAM
« 於: 2004-03-17 10:24 »
看了很多關於 SPAM 的討論,
昨天又看了 OpenWebMail FAQ 裡的 MAIL FILTERING 章節,
有一個主題似乎一直著墨很少, 提出來大家討論看看,
OpenWebMail 的 FAQ 原文如下:

Q: What are "messages with faked smtp"?
A: In short, they are messages coming from mail servers that fake their
   name from other machines.

   Where is a message coming from?

   A message sent from machine A to machine B may have 2 cases:
   a. A ---> M1 ---> M2 ---> B (M1, M2 are mail servers)
      In this case, openwebmail use M1 as the from server.
      Since most of the time, A is windows machine using outlook.
   b  A -------------------> B
      In this case, openwebmail use A as the from server.

   How do we know if a from server fakes his name?

   Each host may have 3 names in the mail header:
   $byas - name used by this server when saying hello to incoming connection
   $relay - name used by this server when relaying mail through other host
   $connectfrom - ip and name detected by other hosts resolved from DNS system when receiving connection from this server

   A from host is faking his name if
   a. $byas doesn't equal to $relay, and
   b. $connectfrom doesn't equal to $relay, and
   c. $connectfrom has different domain than the destitution server B, and
   d. $connectfrom is not private IP

以上的條件要在檢查 Header 的時候就把他檔掉, 該怎麼做呢?  謝謝~~~