Hittade detta hos IBM - min lekmannabedömning är att det verkar vara reverse lookup fast av den sändnande klientens ip kopplat till avsändaradressen. Om inte det fungerar använder man blacklist/whitelist alt skickar mail till avsändaren och ber denne bekräfta sin mailadress, dvs en kombination av traditionella tekniker.
Är det så ni också uppfattar det?
Vet inte om Ny Teknik fått det lite om bakfoten eller om det hänt något ytterligare sen detta publicerades 30/11-2004 (om inte så verkar det ju vara en ganska gammal nyhet).
Citat:
Technically, FairUCE tries to find a relationship between the envelope sender's domain and the IP address of the client delivering the mail, using a series of cached DNS look-ups. For the vast majority of legitimate mail, from AOL to mailing lists to vanity domains, this is a snap. If such a relationship cannot be found, FairUCE attempts to find one by sending a user-customizable challenge/response. This alone catches 80% of UCE and very rarely challenges legitimate mail. A future version will incorporate Sender Policy Framework (SPF) or similar sender identification systems; SPF-enabled domains will not require a challenge. Challenges are sent using a dedicated queue with a short lifetime so it does not get bogged down or interfere with legitimate mail.
If a relationship can be found, FairUCE checks the recipient's whitelist and blacklist, as well as the domain's reputation, to determine whether to accept, reject, challenge on reputation, or present the user with a set of whitelist/blacklist options. A future version will use a real domain reputation system; currently this is implemented as a "whois" look-up to determine the domain's age when it first sent mail to the recipient.
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http://www.alphaworks.ibm.com/tech/fairuce