Bye Bye Spam and Phishing with DKIM?

ppadala writes "While research from PEW Internet (PDF) shows that few users really are bothered by spam, IETF is supporting a public key cryptographic based e-mail authentication mechanism called DomainKeys Identified Mail (DKIM) Signatures . The new spec is supposed to help in fighting both spam and fraud. From Ars Technica: 'DKIM's precursor, DomainKeys, was originally developed by Yahoo. The specifications for DKIM were then extended by an informal group of IT organizations that included companies like Yahoo, Cisco, EarthLink, Microsoft, and VeriSign, among others. It was first submitted by the group to the IETF in mid-2005, but only recently published by the IETF. The spec is still to be incorporated into a more formal draft and submitted for approval, however.'"

Ah, yes the solution of the week

Does anyone have one of those templates where you check off the various reasons as to why this scheme won't work?

Re:Ah, yes the solution of the week

Your post advocates a

(x) technical ( ) legislative ( ) market-based ( ) vigilante

approach to fighting spam. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)

( ) Spammers can easily use it to harvest email addresses
( ) Mailing lists and other legitimate email uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force attacks
( ) It will stop spam for two weeks and then we'll be stuck with it
( ) Users of email will not put up with it
( ) Microsoft will not put up with it
( ) The police will not put up with it
(x) Requires too much cooperation from spammers
(x) Requires immediate total cooperation from everybody at once
(x) Many email users cannot afford to lose business or alienate potential employers
( ) Spammers don't care about invalid addresses in their lists
( ) Anyone could anonymously destroy anyone else's career or business

Specifically, your plan fails to account for

( ) Laws expressly prohibiting it
( ) Lack of centrally controlling authority for email
( ) Open relays in foreign countries
( ) Ease of searching tiny alphanumeric address space of all email addresses
( ) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new taxes
( ) Public reluctance to accept weird new forms of money
( ) Huge existing software investment in SMTP
( ) Susceptibility of protocols other than SMTP to attack
( ) Willingness of users to install OS patches received by email
(x) Armies of worm riddled broadband-connected Windows boxes
( ) Eternal arms race involved in all filtering approaches
(x) Extreme profitability of spam
(x) Joe jobs and/or identity theft
( ) Technically illiterate politicians
(x) Extreme stupidity on the part of people who do business with spammers
(x) Dishonesty on the part of spammers themselves
( ) Bandwidth costs that are unaffected by client filtering
(x) Outlook

and the following philosophical objections may also apply:

(x) Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
( ) Any scheme based on opt-out is unacceptable
( ) SMTP headers should not be the subject of legislation
( ) Blacklists suck
( ) Whitelists suck
( ) We should be able to talk about Viagra without being censored
( ) Countermeasures should not involve wire fraud or credit card fraud
( ) Countermeasures should not involve sabotage of public networks
( ) Countermeasures must work if phased in gradually
( ) Sending email should be free
( ) Why should we have to trust you and your servers?
( ) Incompatiblity with open source or open source licenses
( ) Feel-good measures do nothing to solve the problem
( ) Temporary/one-time email addresses are cumbersome
( ) I don't want the government reading my email
( ) Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

(x) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your
house down!

Not a bad try, though. Usually way more crosses on the form.

Users are not bothered by spam?

I find it difficult to believe that most users are not bothered by spam. As far as I can tell, legitimate email use has been falling dramatically for the past couple years, as people flee the effects of spam, switching to SMS and IM (Jabber, AIM, etc.) Email use within a single corporation remains popular, but home users seem to be abandoning email outright. Some people have given up ordinary email and only use locked-down email inside of social network sites. Spam seems to be killing email. If that doesn't bother people, it's only because they fled email for IM, SMS, and Myspace. If spam follows them, and they have nowhere else to run, they're going to become pretty irate.

Here we go again...

This article advocates a

(x) technical ( ) legislative ( ) market-based ( ) vigilante

approach to fighting spam. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)

( ) Spammers can easily use it to harvest email addresses
(x) Mailing lists and other legitimate email uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force attacks
(x) It will stop spam for two weeks and then we'll be stuck with it
( ) Users of email will not put up with it
( ) Microsoft will not put up with it
( ) The police will not put up with it
( ) Requires too much cooperation from spammers
(x) Requires immediate total cooperation from everybody at once
(x) Many email users cannot afford to lose business or alienate potential employers
( ) Spammers don't care about invalid addresses in their lists
( ) Anyone could anonymously destroy anyone else's career or business

Specifically, your plan fails to account for

( ) Laws expressly prohibiting it
(x) Lack of centrally controlling authority for email
( ) Open relays in foreign countries
( ) Ease of searching tiny alphanumeric address space of all email addresses
( ) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new taxes
( ) Public reluctance to accept weird new forms of money
(x) Huge existing software investment in SMTP
( ) Susceptibility of protocols other than SMTP to attack
( ) Willingness of users to install OS patches received by email
( ) Armies of worm riddled broadband-connected Windows boxes
( ) Eternal arms race involved in all filtering approaches
(x) Extreme profitability of spam
( ) Joe jobs and/or identity theft
( ) Technically illiterate politicians
(x) Extreme stupidity on the part of people who do business with spammers
(x) Dishonesty on the part of spammers themselves
( ) Bandwidth costs that are unaffected by client filtering
(x) Outlook

and the following philosophical objections may also apply:

(x) Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
( ) Any scheme based on opt-out is unacceptable
( ) SMTP headers should not be the subject of legislation
( ) Blacklists suck
(x) Whitelists suck
( ) We should be able to talk about Viagra without being censored
( ) Countermeasures should not involve wire fraud or credit card fraud
( ) Countermeasures should not involve sabotage of public networks
( ) Countermeasures must work if phased in gradually
( ) Sending email should be free
(x) Why should we have to trust you and your servers?
( ) Incompatiblity with open source or open source licenses
( ) Feel-good measures do nothing to solve the problem
( ) Temporary/one-time email addresses are cumbersome
( ) I don't want the government reading my email
(x) Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

(x) Sorry dude, but I don't think it would work.
( ) This is a stupid idea, and you're a stupid person for suggesting it.
( ) Nice try, assh0le! I'm going to find out where you live and burn your
house down!

It's only a server validiation solution

It's only a server validiation solution. DKIM won't stop spam. DKIM will only help validate the identity of the server that is sending you email. Right now I get lots of spam from legitimate Yahoo, Mail.com, and Hotmail servers. DKIM isn't going to stop that it's only going to reinforce what I already know.

Re:It's only a server validiation solution

A quick read of the RFC tells me that this is simply a more computationally-intensive variant of SPF. It still requires rewriting the headers for forwarding, will likely not have the degree of adoption so that anyone in charge of a mail system actually feels confident enough to use it as another weighting factor for testing spam, and still leaves those sitting behind systems that still force users with outside email addresses to use their mail servers. The mere fact that any such system (SPF, DomainKeys or whatever) has to essentially remain completely compatible with older SMTP-based systems means that it really won't solve the problem. The underlying SMTP relay system has problems, and Domain Keys and SPF are just kludgy solutions that really are limited in what exactly they can solve.

few users

spam bothers few users

Dunno about anyone else, but as the admin for our company, I get more complaints about spam than anything other single item I can think of...

Re:few users

Ditto.
The ISP of one of my clients just turned on 'greylisting' and their mail volume dropped 71%, knocking their spam % down to 11% of their new volume.

They would rather spend the budget on stopping spam rather than upgrading their servers. It's that big of a problem.

DKIM will help (until fake 'certificates' show up) but it won't solve the problem. Only flame-throwers, and lots of them, will fix this once and for all.

Will my ISP Quit Blocking Port 25, Finally?

Because keeping me from running a mail server has not done a damn thing to the spammers.

I'll believe in an anti-spam tech when it comes in the Debian repository and I can once again run a mail server. Until then, I'm afraid the spammers will be the first to sign up for any counter measure.

Re:Will my ISP Quit Blocking Port 25, Finally?

Here is what I would like.

If an IP address makes more then X connections to my SMTP port at the same time it gets routed to a teergrube.
If an IP address attempts to send email to Y number of invalid users it gets routed to a teergrube.
If an IP address sends me Z number of spam as marked by spamassassin it gets routed to a teergrube.
If an IP address is on the RBL of my choice it gets routed to a teergrube.

And of course a teergrube which can handle a few hundred simultaneous connections and keep them busy for hours.

If we all had all this then at least we could make a dent in the amount of spam going out.

Darnit!

I'll have to get a second job at McDonalds now..

yahoo press release

http://yodel.yahoo.com/2007/05/22/one-small-step-f or-email-one-giant-leap-for-internet-safety/ [yahoo.com]

It also has some nice background information on DKIM.

--Robert

Prefer SPF

Microsoft, despite its involvement in submitting DKIM to the IETF, is still backing Sender ID and recently bragged that it protects over 8 million domains worldwide.

No Microsoft, SPF is protecting 8 million domains. Nobody publishes SenderID records, you are misrepresenting the intent of millions of domain holders to claim otherwise! What's worse is that the whores in the IETF working group were complicit in this misrepresentation and have the audacity to blame the SPF guys.

I was looking into DKIM earlier today, I much prefer to reject at SMTP time on mfrom or helo. I really don't like the IETF after witnessing the arrogant, egotistical WG assholes ignoring technical merit to play politics. I guess I'll probably refuse to implement DKIM if the IETF are to specially 'bless' it. Standards by committee that co-incidentally fund junkets for a cliche of dick-fiddlers on the dollar of a handful of major corps should be avoided on principle.

Re:Prefer SPF

SPF is protecting 8 million domains

I think the proper phrase is "SPF has cluttered up the TXT field of 8 million domain records, most of them with NEUTRAL because no one has the balls to actually let this creature roam the Internet without a heavy chain".

I believed in SPF about three years ago, but it became very clear that it (and Sender ID too) wouldn't do a damn thing, and Domain Keys seems no different.

Re:Prefer SPF

The problem with putting your eggs in a basket is that it you're putting a helluva lot of trust in a system which is nothing more than a good neighbor policy. A lot of guys I know simply put in SPF records that set them to neutral, because they were ISPs who had clients who were sending from various restrictive networks that blocked them (yes I know, switching ports, SMTP auth and all that ought to do the trick, but we're in the real world here). SPF wasn't perfect, and forwarding was a major failure that was only solved by envelope-rewriting.

I adopted SPF on the domains I ran early on too, not because I thought it would do a damn thing, but because I didn't want to get screwed by some anal-retentive at RoadRunner who decided to start blocking everything that didn't come from an SPF-record holding domain.

SPF, SenderID and DomainKeys probably could have a good deal more success if they were more widely adopted, but they still wouldn't stop some of the big sources of spam. Even with that in place, the mail system is still vulnerable. We were getting such a high volume of distributed dictionary attacks at the place I worked at that we literally had to hide our mail server behind some Postfix proxies which did nothing more than reject hundrds of thousands (and some days millions) of individual attacks per day.

and the winners are

not users by VeriSign and others who will sell hundreds of million domain names encryption keys

is it time to buy shares ?

Sooooo close... but not going to work.

    My initial thought was "Terrific. This really has the potential to eliminate spam." Then I got to looking into the RFC... standard private/public key exchange. But, it allows for individual MUAs to posess the private key, such that they can perform the signature.

    This puts the entire burden of security in the scheme upon the MUA. So any time a machine is infected with the spam-virus of the day, that private key will be sent off to the spammers, who will send out floods of seemingly legitimately-signed email. Instead of just selling valid email addresses to other spammers, they'll sell addresses and domain keys.

    Furthermore, from an administrative perspective, that means that each time one of your user's machines is hacked and the private key compromised, you have to change your public/private keypair, including updating the MUA on *all* of your sender's machines.

    Forcing signing upon the MTAs eliminates much of that work (and hopefully the security exposure), but forces inconvenience on a good number of users. It's a tradeoff I'd be willing to make, but the RFC doesn't seem willing to do so.

Re:Sooooo close... but not going to work.

You've come close to what I arrived at in the last few months of my job working for an ISP, that all these kludgy attempts to beef up SMTP would always be fatally flawed unless we (and by that I mean Joe Average and admins) was prepared for inconveniences. That means putting an end to straight-out forwarding, because that pretty much busts everything without the major overhead of rewriting the headers. It means locking down the servers themselves and not expecting some "good neighbor" protocol to somehow magically take care of the problem. As someone else has pointed out, how is DomainKeys any different than PGP signing, which has been around for two decades now. Even if we went to DomainKeys or PGP, it still wouldn't stop all those zombies out there from happily sending signed spam. It means that distributed dictionary attacks would have to come in with a legitimate address from the source network, but I doubt the spammers are going to give a damn about that.

The problem with spam is that it isn't just an email problem. If it was, then we'd all have had this beat a long time ago.

I am trying DKIM

DKIM is great except, AFAIK:

1) There's still no way of saying "my domain always signs email with DKIM, so no signature means forged mail". At least I couldn't figure it out.
2) Mailing lists add a footer which messes with the signature.

As a consequence DKIM at the moment is completely useless since even though all my emails are signed, spammers/phishers can simply not put the DKIM signature and DKIM wouldn't know if the email was forged or not.

Furthermore, DKIM is reporting that a lot of valid emails posted to mailing lists (mostly gmail ones) are forged.

If these 2 problems are solved, I think DKIM could be the best way of building a reputation system to stop spam almost completely.

The first problem is easy to solve (just add a new flag to the DKIM DNS record), the second one could be solved by *requiring* the DKIM-verification software to discard everything following the length of the signed body (at the moment it's optional), and by *requiring* to specifiy said length (dkimproxy can't do that, AFAIK).

Only two ways this can go

And they both fail.

Either the domain owner controls and administers the key, in which case spammers (who already use automated bots to registers hundreds, if not thousands, of domains per day) will simply add a new subroutine to the domain registration bot to add in the key, thus ensuring the delivery of their spam.

Or someone else controls your email, which mean nobody with any sense will buy in to it.

Either way, it's useless for combatting spam, as was DomainKeys and SPF.

Metric on number of responses to spam

Page 5 of the PEW Internet study reports that "...only 4% of email users admitted to action that keeps the spam industry viable, which is ordering a product or service from an unsolicited email. This number has always been low; it was 7% in 2003, 5% in 2004, and 6% in 2005."

These figures are interesting because there is often speculation about these numbers during conversations about the financial viability of being a spammer. The article suggests that these figures are "low" but they are much higher than the "back of the envelope" estimate of 1% that I usually see people use when guessing. It is going to be difficult to stop the spam problem when people keep buying things from spammers. Even if technical solutions like DKIM have some degree of success, such a high response rate to spam gives an obvious incentive to spammers to continue to find work-arounds.

we still haven't solved junk snail mail

What makes you think that this is going to do anything for junk email. Until the burden of the spam is placed on the sender and not the receiver this problem will never go away. See http://cr.yp.to/im2000.html [cr.yp.to] for a workable solution.

My solution...

click [mailto]

The reason why I don't use DKIM or recommend it

Every message *received* needs to be run through an expensive cryptographic routine. If you have high incoming mail volume, just watch your server load skyrocket when DK/DKIM is turned on. You also have to completely accept the entire message before DKIM can be used. With SPF, you can simply reject after the envelope-sender is specified and before the headers and data.

explode button

until there is a button which i can click on each email and cause the sender of the mail to explode an a bloody rain of guts and gore, spam will not end.

No better then SPF

With SPF, you validate which mail server your getting mail from.

with DKIM, your validating which mail server and a heavy crypto message to compute with SPF.

SPF is only going to fail if you go to a spoofed dns server, or if your mail server is rooted. So where do you get the DKIM sig from. What if it's spoofed?

To make validating your mail server work, all the mail servers have to have SPF entries. The same with DKIM. If I had to vote for one or the other, SPF is good enough. DKIM costs to much, I don't want to have to build any more email machines then I have to. Keeping them all in sync is to much of a pain.

barking up the wrong tree

I think the OpenBSD guys have the best solution to spam bar none. Rather than adding fancy verification, authentication, or filtration layers, they engage in a technique to make the spammers hurt: tar-pitting. Why not force spammers to put up with an SMTP server that is so slow that it causes them to choke. The best solution for fighting spam is not through processor expensive filtration or key decryption process but through a combination of greylisting, greytrapping, and greyscanning. These methods bring about measurable results. This is ingenious. I have set up an OpenBSD spamwall at my father's business. We have gone from several hundred spam messages per day to only 10 per week. In a 24 hour period we were hit with 2000 smtp connection attempts. Of those 1992 of them gave up. The biggest complaint I have recieved was that they were not getting enough spam and there was concern that legitimate email might be lost. Our spam wall has been in service for a month without problems. The system is not perfect, but a drastic reduction is realized. These methods hurt the spammer and if enough people employ them, spam may become a thing of the past. The absolute worst thing that could happen is that a legitimate email might be delayed by 4-6 hours.

are they kidding?

>>"While research from PEW Internet (PDF) shows that few users really are bothered by spam,"

ARE THEY JOKING? few users are bothered by spam??? Everyone I know, both personally, and at work, gets bombarded by 100s of spam email messages a day and is getting quite irate. The discussion about how useless email has become due to spam comes up almost on a daily basis amont me and my associates. Email was a GREAT way to communiacate, but has quicly become quite useless due to all the spam and the associated filtering, etc...

They must be kidding when they say it only bothers a few people, and I would like to know who IS NOT bothered by spam.

-farshad

I still like HashCash better

Instead of trying to validate mail, just make it computationally expensive to send. Anyone with a compromised Windows box will know immediately because it will be running at 100% CPU utilization constantly. Even if they don't have the technical expertise to know what's wrong, they'll still have an idea that it's broke.

How come these guys never realize that if a scheme can't stop bots, it's worthless. Also, all these fancy schemes are bound to fail because they try to make fighting spam the lever to get everyone on earth to register with them so they can be the toll collector for the future of email.

The only problem with HashCash is that the biggest detractors will be the providers of free email services. They happen to control most of the mailboxes. They don't want their service to become more expensive, and they don't want to see all their hard work not turn into some future monopoly.

just one word

I just want to say one word to you. Just one word.

Botnets.

www.dkim.org

Any spam solution that uses Comic Sans on its web site [dkim.org] is no spam solution.

Maybe that should be added to the spam solutions form?

solution to phishing: bi-directional login

A good solution for spam, phishing etc would be the bi-directional login.

As it is right now, we users log in a server and use the available services, but we don't know if the server is what it claims it is. The server may know us because we have submitted a username and password, but we don't know if the server is the correct one. Right now login is uni-directional.

One solution to phishing would be bi-directional login: not we users submit a password to the server, but the server submits a password to us. If both submissions are successful, then the operation could proceed.

The biggest problem with domain keys

I work in the email security industry, and the biggest problem with domain keys is that hardly anyone uses it.

Yahoo: check
eBay: check
PayPal: check

My bank? Nope.
My wife's bank? Nope.
Any other bank whose legit mail I have seen? Nope.

Domain keys are an excellent way to fight phishing, and they really help in that area. They are less helpful on fake Yahoo spam because a lot of people set their From address to be their Yahoo address even when not sending through Yahoo.

eBay and PayPal phishing is easy to nail because of the fact that they do use domain keys. Bank phishing is tougher because few if any banks are using them. If they start doing it, fighting phishing be easier. DK(IM) is not a magic bullet, but it's one more thing we can use.

Why FastMail.FM stopped testing for DomainKeys

In this forum post [emaildiscussions.com] Rob Mueller of Fastmail.fm explains why they stopped using the SpamAssassin plugin for DomainKeys.