Distributed Checksum Clearinghouse (also referred to as DCC) is a method of
spam
Spam most often refers to:
* Spam (food), a consumer brand product of canned processed pork of the Hormel Foods Corporation
* Spamming, unsolicited or undesired electronic messages
** Email spam, unsolicited, undesired, or illegal email messages
...
email detection.
The basic logic in DCC is that most spam mails are sent to many recipients. The same message body appearing many times is therefore bulk email. DCC identifies bulk email by calculating a
fuzzy checksum on it and sending that to a DCC server. The server responds with the number of times it has received that checksum. An individual email will create a score of 1 each time it is processed. Bulk mail can be identified because the response number is high. The content is not examined. DCC works over the
UDP protocol and uses little
bandwidth.
DCC is resistant to
hashbusters
A hash buster is a program which randomly adds characters to data in order to change the data's hash sum.
This is typically used to add words to spam e-mails, to bypass hash filters. As the e-mail's hash sum is different from the sum of e-mail ...
because "the main DCC checksums are fuzzy and ignore aspects of messages. The
fuzzy checksums are changed as spam evolves"
Distributed Checksum Clearinghouses official website
/ref> DCC is likely to identify mailing lists as bulk email unless they are white listed. Likewise, repeatedly sending the same email to a server increases its number in the server, and, therefore, the likelihood of it being treated as spam by others.
History
According to the official DCC website:
The DCC is based on an idea of Paul Vixie and on fuzzy body matching to reject spam on a corporate firewall operated by Vernon Schryver starting in 1997. The DCC was designed and written at Rhyolite Software starting in 2000. It has been used in production since the winter of 2000/2001.
References
External links
*
{{Spamming
Anti-spam