Intel researchers are exploring ways to improve on existing anti-spam systems, to reduce false positives (legitimate email that is mistakenly tagged as spam) and false negatives (spam that is not filtered out). To determine if a given message is spam, many anti-spam systems extract tokens such as words from the message. Despite the sophistication of some systems, it's difficult to determine if a message that includes, say, "mortgage" is spam, or an email from a friend who just purchased a home. Users can create whitelists to tell the system to allow mail from certain parties, but manually creating such lists is a time-consuming process.
Intel researchers are investigating a more effective whitelist system that leverages a user's email social network. Under this "friends of friends" approach, users automatically whitelist email addresses that the user's correspondents consider valid. This approach eliminates false positives among the user's immediate and one-hop correspondents, making email reliable among this group of people. Researchers are addressing the privacy concerns of sharing personal whitelist information with other people and forgery (spammers pretending to be one of the people on the user's whitelist) through cryptography and secure protocols.
To catch spam from unknown senders, researchers are also developing a distributed spam rejection system based on collaborative filtering. Under this approach, users in the email network "vote" on whether a message is spam. Once several users declare that a particular message is spam, other users can automatically filter it as such. Traditionally, distributed collaborative filtering has not addressed malicious users who try to distort the voting by submitting multiple votes or by preventing other users' votes from being counted. Intel researchers are exploring efficient techniques to deal with malicious users based on social networks.
Haifeng Yu, Michael Kaminsky, Phillip B. Gibbons, and Abraham Flaxman. SybilGuard: Defending Against Sybil Attacks via Social Networks. In Proceedings of the ACM SIGCOMM Conference on Computer Communications (SIGCOMM 2006), Pisa, Italy, September 2006. Original Paper: [PDF] Expanded Technical Report [IRP-TR-06-01]: [PDF]
Scott Garriss, Michael Kaminsky, Michael J. Freedman, Brad Karp, David Mazières, Haifeng Yu. Re: Reliable Email. In Proceedings of the 3rd Symposium on Networked Systems Design and Implementation (NSDI'06), San Jose, California, May 2006. [PDF]