Kevin Werbach advocates the use of white-lists to battle spam. This will, in effect, change email from an open system to a closed system. He wrote about this in Slate (November 18,2002):
Whitelists typically allow e-mail from everyone in a user’s existing address book. Other, unknown senders receive an automated reply, asking them to take further action, such as explain who they are. Or senders may be asked to identify a partially obscured image of a word. A person can make out the word, but automated spammer software can’t.
Whitelists are rare today, but they will become more common. The relentless growth of spam guarantees it. A filter that catches 80 percent of spam sounds great, and it is great if you get 10 spams a day. But when you get 500 a day, that same filter leaves you sorting through 100 opportunities to Make Money Fast!!!!!
Like it or not, the only way to kill spam is for an element of e-mail to die as well. There’s always been something charming and casual about e-mail. The informality comes through in the style people use to write messages, but also in where they send them. You’ve probably sent an e-mail to someone you’d never call on the phone, approach in person, or even write a letter to. Losing this aspect of e-mail is a shame, but it’s inevitable. E-mail will become more like instant messaging, with its defined “buddy lists.”
E-mail’s openness is doomed when faced with massive traffic and a few bad actors. The next time you try to reach out and touch someone electronically, you may need to know who that person is. Otherwise, you might be reaching out to no one.
An application which builds on Kevins idea further is Tagged Message Delivery Agent (TMDA):
TMDA is an open source software application designed to significantly reduce the amount of SPAM (Internet junk-mail) you receive. TMDA strives to be more effective, yet less time-consuming than traditional SPAM filters. TMDA can also be used as a general purpose local mail delivery agent to filter, sort, deliver and dispose of incoming mail.
The technical countermeasures used by TMDA to thwart SPAM include:
– whitelists: accept mail from known, trusted senders.
– blacklists: refuse mail from undesired senders.
– challenge/response: allows unknown senders which aren’t on the whitelist or blacklist the chance to confirm that their message is legitimate (non-SPAM).
– tagged addresses: special-purpose e-mail addresses such as time-dependent addresses, or addresses which only accept certain kinds of communication. These increase the transparency of TMDA for unknown senders by allowing them to safely circumvent the challenge/response system.
This combination was chosen based on the following assumptions about the current state of SPAM on the Internet:
1. You cannot keep your email address secret from spammers.
2. Content-based filters can’t distinguish SPAM from legitimate mail with sufficient accuracy.
3. To maintain economies of scale, bulk-mailing is generally: an impersonal process where the recipient is not distinguished. and a one-way communication channel (from spammer to victim).
4. SPAM will not cease until it becomes prohibitively expensive for spammers to operate.
Tomorrow: My Solution Ideas
TECH TALK The Death and Rebirth of Email+T