Spam-proofing the mail system [LWN.net]

Spam-proofing the mail system

Posted Dec 18, 2003 4:48 UTC (Thu) by freemars (subscriber, #4235)
Parent article: Spam-proofing the mail system

The systems described concentrate on identifying the source of the email. I think a more direct approach would be an extension to SMTP requiring a micropayent to the recipient.

At some point as two computers are negotiating to set up a SMTP session the recipient computer can request a micropayment. If the originating computer doesn't comply it gets a brush-off message and the connection is closed. If the originating computer sends a micropayment token the receiving computer immediately takes it to the bank. If the bank OKs the payment the email body is accepted. Otherwise the connection closes with a brush-off message.

In the traditional ISP model this will take place at the ISP level. The customer will eventually log in and retrieve mail. It is vitally important the micropayment get passed on to the final recipient; that's the only person who can tell if an email is legetimate or if it's spam.

When you log into your account and get your mail, it will come with dime-sized credits attached. As you read your mail, you get to decide: if a message is spam, you keep the dime. If it is legetimate, you return a micropayment to the sender, and probably add the sender to a whitelist. (Don't want to refund the payment? You run the risk of getting labeled a deadbeat, and never getting email from anyone.)

Whitelists and blacklists for each email address would be kept at the ISP, and are essential to running this system efficiently. If someone is on your whitelist, the request for a payment portion of the SMTP session never takes place, saving the bank overhead for two transactions (the payment and the refund). Whitelists allow good things like mailing lists to continue operating without a major financial hit. If a sender is on your blacklist your ISP will happily accept the micropayment and message, but silently disgard the latter.

This plan needs several things to work:
**** SMTP and user mail software which supports micropayments.
**** A low-overhead micropayment system. The volume of micropayments this plan would generate would allow the kind of automated procedures needed to make a low-overhead system practical.
**** An RFC setting out how the protocols work
**** Antitrust exemption from the US Congress allowing ISPs to work together to install the plan in a unified manner. If the 10 largest US ISPs announced that after a given date no email would be accepted from strangers unless it complies with RFC####, it would become the de-facto world standard on that date.

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Anonymous e-mail?

Posted Dec 18, 2003 5:38 UTC (Thu) by lovelace (subscriber, #278) [Link]

Doesn't your system preclude the possibility of sending anonymous e-mail (since every e-
mail account must be hooked up to a bank account)? And what about people who don't have
a bank account? While I hate spam as much as the next person, it seems to me your system
gives away too much.

Anonymous e-mail?

Posted Dec 18, 2003 14:53 UTC (Thu) by tonnesen (guest, #3589) [Link]

Any of these proposals would limit the possibility of sending anonymous e-mails. What would we lose if, say, the domain keys proposal was limited? A whistle blower couldn't send an e-mail to a newspaper without worrying that he could be identified later? I'm sure there are many other instances where anonymous e-mail is desirable. How is anonymous e-mailing done now? You can't just forge the sender. The originating IP address will still show in the headers and be traceable.

Should anonymous e-mailing be a pay-as-you-go system? You can send mail from your account at wekeepyouhidden.com which you pay $20/month for.

What about the "free" e-mail systems like hotmail, yahoomail, etc. They'll presumably get domain keys, and continue allowing spamers to send spam through them. What percentage of current spam is sent through these systems now? They wouldn't solve the anonymity problem because, as far as I know, they all attach the originating IP address to the messages they send.

Should anonymous e-mailing be a pay-as-you-go system? You can send mail from your account at wekeepyouhidden.com which you pay $20/month for. My gut tells me this is the only way to get true anonymity now (short of cracking computers and sending from there, but I can't exactly endorse breaking the law as a solution).

My feeling is that blacklists like SpamCop et al would be significantly more effective under the domain keys proposal. Blacklist systems could easily link all messages from one domain together and aggregate the complaints they receive about that domain.

Anonymous e-mail?

Posted Dec 18, 2003 18:06 UTC (Thu) by iabervon (subscriber, #722) [Link]

Anonymous email would still be possible under the SPF system, at least,
by simply permitting mail from hosts that don't claim to be anyone in
particular. Such email wouldn't be verified at all, since it didn't claim
to be anything in particular. Most people would just throw it away, but
anonymous tip lines wouldn't (since they wouldn't get anything else,
obviously), and spammers wouldn't tend to spam such addresses anyway (do
spammers really want to reach investigative reporters at their work?).

Furthermore, if people are actually using an anonymizing network, the
email will come out with a perfectly valid and legitimate address which
simply can't be tracked back to the sender, and is authenticated as being
an anonymous message from this remailer. These systems are generally
pseudonymous, in any case, so that the original sender can send
additional messages authentically, and these systems would merely
authenticate the pseudonym. Again, this mail would be filtered by most
people, but would get through to people who intend to pick up anonymous
tips.

Yes, anonymous e-mail

Posted Dec 18, 2003 16:03 UTC (Thu) by freemars (subscriber, #4235) [Link]

Doesn't your system preclude the possibility of sending anonymous e-mail (since every e-mail account must be hooked up to a bank account)? And what about people who don't have a bank account?

I believe in the value of anonymous email, and believe this plan supports it better than the ones suggsted above. While it's true the ISP must be hooked up with a bank an individual sender needn't be. Imagine a system where you go to a convenience store and buy a CD with 200 email stamps worth a dime each. The CD might cost $25 -- $20 for the value of the stamps, $2.50 markup for the store, $2.00 for the bank, and $0.50 for the CD, packaging & distribution. You could pay cash for the CD and take it to your local Starbucks/Internet Cafe to send emails.

Since you're trying to be annonymous, you forge your return address, so you never get your rebate. It either gets lost in cyberspace (and never cashed in; the bank thanks you) or goes to your favorite charity.

A poor person might have to scrape to come up with the $25 purchase price, but doesn't need to jump through all the hoops of getting a bank account. If most of your mail goes to people who know you -- and have you on their whitelists -- your initial supply of stamps will last a long time.

Spam-proofing the mail system

Posted Dec 18, 2003 5:51 UTC (Thu) by sfeam (subscriber, #2841) [Link]

Your proposal sounds counterproductive. As you describe it, the spammer only gets charged if I read the spam. The spammer might well be OK with that, but my goal is to never see the spam in the first place. The more successful people become at filtering, the less penalty is applied to the spammer. Surely that is not what you intended.

Spam-proofing the mail system

Posted Dec 18, 2003 10:16 UTC (Thu) by ekj (subscriber, #1524) [Link]

This is true, on the surface.

But the thing is, the requirement alone to attact a dime to every outgoing spam is likely more than enough to make spamming a non-issue.

If you have to attach say $0.10 to every outgoing message, then even if 90% of the spam is never read so you eventually get the money back (I assume there'd be a timeout of some sort), you'd still be paying $0.01 a message.

Sending a million spam-emails at this rate would cost you $10K. Personally, I think this is low. Because the economics of reading spam would completely change. I would, for example, happily read and delete spam if I knew it would gain me, and cost the spammer, $0.10 for each one. Why, with my current load, and assuming I could process one spam a second, I would make around $5 a day, and would be spending less than 10 minutes to do so.

In practice offcourse, the chanse of any spammer paying me, even a single cent, for me to read their message is miniscule.

Spam-proofing the mail system

Posted Dec 19, 2003 1:58 UTC (Fri) by giraffedata (subscriber, #1954) [Link]

Hear hear. Between my automatic deleters and my morning manual deletion ritual, I determine to be spam and delete about 200 messages a day. The morning ritual takes about two minutes. Programming the automatic deleters, an hour a month. Well worth $20. Of course, most of those spams would not be in my mailbox at all if they had to have $.10 attached. Based on the fact that I never buy anything and never fall for scams, I doubt I'd get more than a few spams a week.

Spam-proofing the mail system

Posted Dec 18, 2003 14:52 UTC (Thu) by freemars (subscriber, #4235) [Link]

The more successful people become at filtering, the less penalty is applied to the spammer. Surely that is not what you intended.

Indeed that's not what I intended. Filtering spam would have the same effect as what I described as blacklisting; accept the payment for the spam but throw away the message unread. It costs them a dime but they have no idea if the message was ever seen by human eyeballs.

Spam-proofing the mail system

Posted Dec 19, 2003 0:15 UTC (Fri) by Ross (subscriber, #4065) [Link]

Who would fund mailing lists? I'm sure you couldn't depend on every user
subscribed to a list to return the funds (no to mention the list admin is
out those funds until they are returned? This would be a huge problem for
large mailing lists.

Who would manage the micropayments? Would we all get PayPal (shudder)
accounts? What prevents micropayments from being stolen by ISPs
or someone hijacking accounts?

Spam-proofing the mail system

Posted Dec 19, 2003 2:00 UTC (Fri) by giraffedata (subscriber, #1954) [Link]

With a decent micropayment system (as postulated), it would be easy to charge minuscule subscription fees for mailing lists, which would cover the occasional non-refund and the transaction fees.

Spam-proofing the mail system

Posted Dec 19, 2003 4:50 UTC (Fri) by brouhaha (subscriber, #1698) [Link]

Who would fund mailing lists?

In a micropayment email system, the recipient sets the amount of the micropayment, which can vary depending on the sender. Most people would whitelist their friends and charge nothing. Presumably they would do this for mailing lists as well, and if the mailing list attempted to deliver to a recipient demanding a payment, would simply drop that recipient from the list.

That leaves open the possibility of a spammer masquerading as a list server, but other anti-spam techniques such as SPF easily thwart such misrepesentation.

It also would be possible to set the amount fairly high, but refund it in the case of unsolicited but non-spam email. For instance, I'd probably set my software to charge at least $0.25, and perhaps as much as $1, for unsolicited email from non-whitelisted senders. But for non-spam email, for instance people inquiring about free software I've written, I would refund it.

Probably a fee as low as a penny would discourage a lot of spam, but having the fee higher would serve to also discourage email from students that want me to do their EE or CS homework for them. (I get such email routinely as the result of having a web page about PIC microcontrollers, despite the web page clearly stating that I don't have time to offer free help.)

Spam-proofing the mail system

Posted Dec 19, 2003 13:46 UTC (Fri) by freemars (subscriber, #4235) [Link]

Who would fund mailing lists? I'm sure you couldn't depend on every user subscribed to a list to return the funds (no to mention the list admin is out those funds until they are returned? This would be a huge problem for large mailing lists.

Mailing lists would depend on whitelists. (This means that any new software supporting micropayments must support whitelists also. Because the whitelist would be stored at the ISP both the userland mail-reading software and the ISP SMTP software would have to support whitelists.)

Mailing lists could operate much like current "double opt-in" lists do today... when you subscribe the list sends a 'welcome' email which asks you to whitelist the mailing list address. When you do (sending a rebate to the list) the software notices and adds you to the list. To remove yourself from a list, simply remove it from your whitelist. When the list software gets a request for a micropayment (not whitelisted) it declines to pay and removes the recipient from the list of subscribers.

Who would manage the micropayments? Would we all get PayPal (shudder) accounts? What prevents micropayments from being stolen by ISPs or someone hijacking accounts?

You've found the potential showstoppers. Ideally, there would be a few banks in the business so there would be some pressure on them to hold rates down. It will be up to individual ISPs to decide if they will accept payments from Fred's Bank (where Fred's Bank might be located in some unsavory nation). I would expect ISPs would quickly settle on accepting payments only from member banks of some International Collaboration of Cooperative Micropayment Banks, all of which agree to the following standards:
**** All payments are made in (what, Euros? Something stable)
**** All payments may be converted to [list of currencies] with a conversion rate set by [someone's daily conversoin rate index]
**** All payments can be redeemed at full face value (the sender pays the bank's mark-up, whatever it is)
**** All member banks will honor payments from any member bank (the cost of this service is built into the sender's mark-up)
**** All member banks use a standard set of protocols when clearing payments
**** ???

I'm hoping a few companies -- probably current-day banks -- would step up and offer such a micropayment system. If all email were to convert to a micropayment system there would be enough use to justify setting up the kind of heavily automated system that would be needed to be affordable.

Spammers will no doubt try to hijack computers which have access to email 'stamps'. Cautious people will not store large numbers of 'stamps' on their computers. Prediction: someone will decide it's a really cool idea to keep the user's credit card information in the computer so the software can automatically buy extra email 'stamps' from the International Bank of Microsoft as needed -- some people will get burned.

"Bad" ISPs stealing people's micropayments ... you ask tough questions ... perhaps the legislation protecting ISPs from anti-trust lawsuits should only apply to those which pass on 100% of the micropayments to their customers. "Bad" ISPs could also mess with customer whitelists, but I don't see what they would gain from doing that.

Spam-proofing the mail system

Posted Dec 28, 2003 20:07 UTC (Sun) by rogblake (guest, #18258) [Link]

You seem to be forgetting that not everyone has a bank account, or a credit card. It looks like your solution to the spam problem would have the side effect of not allowing such people to use email at all!