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| 2004 - Pérennisation |
  Spam, a personal and professional annoyance
[10 mn of reading - published 5/10/2004 4:05:08 AM - Target : Débutant]
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Author
3. Anti-spam methods
3.1. Client side
Some ISP try to learn how to prevent spam to their customers, like avoiding giving email address to anyone or on any website, or avoiding opening "weird" emails, to prevent contamination or telling the spammer its mail has been read.
Most mail clients include anti-spam filters tools, some of them being more efficient than some others. Some of them (e.g. Mozilla Thunderbird) try to "learn" how to recognize a spam, by asking the user to manually tell which mail is a spam.
3.2. Server side
There are also anti-spam filters that can be installed on mail servers, like Spam Assassin (a "bayesian filter" system). This one is very powerful and used over the world; it uses a "score" system: some criterias (no "To:" field, no subject, some specifical words in the text) bring points, and Spam Assassin eliminates or marks mails reaching a certain amount of point. Unfortunately, it can block legitimate mails by mistake, as well as ignoring real spams.
Click on the image to display the whole screenshot
Blacklists are the other popular systems: lists of open mailservers (don't asking for login/password to send mails, or not checking sender's IP's domain) or well-known spamming mailserver, and updated by a few people (mostly providers) often by a website. This method is more reliable, but requires regular updating. Both systems can be used at the same time, without any side effect.
3.3. Methods currently being researched
Some companies are trying to make their own system becoming standards.
AOL wants to implement a DNS protocol extension: a new DNS record type, telling which mailserver(s) are authorized to send mails from the domain. The biggest side-effect is the obligation to mail from the domain's mailserver, making mail redirections hard to use.
Yahoo's system brings the same problem: a new DNS record type giving the domain's public key, which will be used to authentify mails sent from the domain, using a signature that the mailserver will automatically add to each mail it sends.
Microsoft wants to make computers calculate a little mathematical question when they send a mail, which will last an insignifiant amount of time for a normal user, but will take much time for a spammer, sending millions of mails.
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184 Hits
Benoit RICHTER
[30 mn of reading - published 5/10/2004 4:01:11 AM - Target : Débutant]
[20 mn of reading - published 5/10/2004 1:11:23 AM - Target : Confirmé]