Simon Byrnand wrote: > Why would anyone submit the SA list to DCC ? The only people receiving the > SA list should be people who subscribed to it, and would have no reason to > go submitting it to DCC, so I don't follow your reasoning...
I don't know how to make this sound less quib than just by saying that it is not. Please review the DCC documentation. I feel confident that you have not read it because you could not have missed reading this there. DCC is not about spam. It is about bulk mail. But knowing the bulkiness of it can be a good indicator of a message being spam. Which makes the information that DCC provides very effective in the battle against spam. By taking that stance they avoid all of the trust issues which have plagued Razor. Which tidies up the problem considerably. Here is one executive summary version: http://www.rhyolite.com/anti-spam/dcc/dcc-tree/dcc.html DESCRIPTION The Distributed Checksum Clearinghouse or DCC is a cooperative, distributed system intended to detect "bulk" mail or mail sent to many people. It allows individuals receiving a single mail message to determine that many other people have received essentially identical copies of the message and so reject or discard the message. It can identify some unsolicited bulk mail using "spam traps" and other detectors, but that is not its focus. [...] How the DCC Is Used The DCC can be viewed as a tool for end users to enforce their right to "opt-in" to streams of bulk mail by refusing bulk mail except from sources in a "white list." White lists are the responsibility of DCC clients, since only they know which bulk mail they solicited. [...] A DCC server computes a lower bound on the total number of addresses to which a message has been sent by counting checksums reported by DCC clients. Each client must decide which bulk messages are unsolicited and what degree of "bulkiness" is objectionable. Client DCC software marks, rejects, or discards mail that is bulk according to local thresholds on target addresses from DCC servers and unsolicited according to local white lists. DCC servers are usually configured to receive reports from as many targets as possible, including sources that cannot be trusted to not exaggerate the number of copies of a message they see. Any mail sent to what a client individually considers a "spam trap" can be seen as "definitely bulk," but not necessarily unsolicited by other DCC clients. An end user of a DCC client angry about receiving a message could report it with 10,000,000 separate DCC packets or with a single report claiming as many targets. An unprincipled user could subscribe a "spam trap" to mailing lists such as those of the IETF or CERT. Such abuses of the system area not problems, because much legitimate mail is "bulk." You cannot reject bulk mail unless you have a white list of sources of legitimate bulk mail. http://www.rhyolite.com/anti-spam/dcc/FAQ.html#mark-only Why is mail from my favorite mailing list marked with an X-DCC header line that says it is spam? Sources of solicited bulk mail including mailing lists to which you have subscribed should usually be in your DCC client white list so that they receive no X-DCC header lines. Why do legitimate mail messags have X-DCC header lines that say they are "bulk"? There are several possible causes of such problems. The first and most obvious is that the mail is solicited bulk mail and that the source needs to be added to your white list. [...] How can I avoid polluting databases of DCC servers with checksums of my mail that is not spam? Reports of checksums with white list entries in your server's database are not flooded to its peers. The checksums of messages white-listed with entries in local dccm or dccproc white lists are not reported to DCC servers. It is good to add entries to DCC server and client white lists for localhost, your IP address blocks, and your domains if you know that none of your users will ever send spam. However, in the common mode in which the DCC is used, no checksums of mail are pollution. Checksums of genuinely private mail will have target counts of 1 or a small number, and so will not be flooded by your server to other servers. Strangers will not see your private mail and so will not be able to ask any DCC server about the checksums of your private mail. On the other hand, the DCC functions best by collecting reports of the receipt of bulk mail as soon as possible. That implies that it is generally desirable to send reports of all mail to a DCC server. The DCC flooding protocol does not send checksums with counts below a DCC server's bulk threshold to other servers. Bob
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