Greylisting - Francais

Je considérais le Greylisting comme un sujet assez important pour traduire mon article sur ce mécanisme anti-spam:

Voici une explication du "Greylisting", un mécanisme très efficace contre les spams:

  • Basé sur des "triplets" (adresse de courriel de l'expéditeur, adresse de courriel du destinataire, adresse IP du serveur d'origine).
  • Quand un serveur recoit une connexion SMTP d'un autre serveur, il vérifie le triplet. Si le triplet est connu, le message continue son chemin. Sinon, le serveur refusera la connexion à l'aide d'un message SMTP 450 (échec temporaire), donc disant au serveur d'origine: Je ne peux accepter le message présentement, veuillez revenir plus tard.
  • La plupart des serveurs de courriel respectent cette règle (RFC821) et ré-essayent une connexion quelques minutes plus tard (Microsoft Exchange et Hotmail: normalement 1 minute, Yahoo: ~5, Sendmail: ~7, Postfix: ~1, Exim: ~3). Les délais sont normalement minimes, si perceptibles.
  • Lorsque le serveur ré-essaye, le triplet est maintenant connu, alors le message est accepté et le triplet est gardé en mémoire pour une certaine durée. De cette manière, si le même expéditeur envoie un message au même destinataire le lendemain, aucun délai ne devrait être imposé et la mémoire est prolongée d'un jour.
Il y a des avantages à deux niveaux:
  • La quantité de spams qui finissent dans la boite de courriel des usagers est réduite considérablement (exemple).
  • La charge sur les ressources matérielles sont moindres. En effet, la plupart des engins anti-spam conventionnels sont tres exigeants envers les ressources (CPU/mémoire,E/S disque). Lorsque le Greylisting bloque un spam, il le fait à la transaction SMTP, donc le message n'atteint jamais les systèmes qui sont les plus exigeants pour les ressources matérielles.
Si vous désirez obtenir plus d'information à ce sujet, je vous recommande les liens suivants:

http://www.greylisting.org
http://projects.puremagic.com/greylisting/
http://en.wikipedia.org/wiki/Greylisting

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