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Comparison of Bayesian POP3 Spam Filters 326

kreide writes "Spam e-mail has become an ever increasing problem, and these days it is next to impossible to use e-mail without receiving it in large amounts. Although various techniques exits to combat the problem, spammers seemed to be winning the war - until a new, powerful weapon appeared on the scene: Bayesian filters, our last, best hope for spam-free inboxes. In this review I compare POP3 based bayesian spam filters." We did an Ask Slashdot on this a few weeks ago.
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Comparison of Bayesian POP3 Spam Filters

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  • Nitpick... (Score:2, Insightful)

    by 1029 ( 571223 )
    I just sure as hell hope he meant "latest, best hope", because anyone who thinks bayesian is the LAST best hope doesn't understand CS technology at all. And such a person sure as all hell shouldn't be given an audience on /.
    • Re:Nitpick... (Score:5, Interesting)

      by spongman ( 182339 ) on Monday August 11, 2003 @06:22AM (#6663995)
      Actually SpamBayes isn't bayesian at all. It uses a chi^2-based algorithm which was shown in (the extensive spambayes team's) tests to be superior to regular bayesian filtering.
      • Re:Nitpick... (Score:5, Informative)

        by spongman ( 182339 ) on Monday August 11, 2003 @07:01AM (#6664097)
        Here's a bit from the excellent SpamBayes background page [sourceforge.net]:
        A remarkable property of chi-combining is that people have generally been sympathetic to its "Unsure" ratings: people usually agree that messages classed Unsure really are hard to categorize. For example, commercial HTML email from a company you do business with is quite likely to score as Unsure the first time the system sees such a message from a particular company. Spam and commercial email both use the language and devices of advertising heavily, so it's hard to tell them apart. Training quickly teaches the system all sorts of things about the commercial email you want, though, ranging from which company sent it and how they addressed you, to the kinds of products and services it's offering.
  • by fr0z ( 658466 ) <[fr0z] [at] [myrealbox.com]> on Monday August 11, 2003 @04:10AM (#6663652) Homepage
    I still believe that we should have a hunting season for spammers, just like we do for ducks...
    • by frovingslosh ( 582462 ) on Monday August 11, 2003 @04:16AM (#6663667)
      I still believe that we should have a hunting season for spammers, just like we do for ducks...

      No, it should be longer, if not all year long.

      • by dtfinch ( 661405 ) * on Monday August 11, 2003 @04:28AM (#6663704) Journal
        You know, computer crimes are considered terrorism under the USA PATRIOT Act. Until that silly law gets repealed, lets hunt down those terrorists for their, umm, denial of service attacks against innocent email users, bandwidth theft, failure to provide real opt-out links, sending email advertisements with fake return addresses, presenting obscene material to minors, etc...
      • by mirko ( 198274 ) on Monday August 11, 2003 @04:42AM (#6663747) Journal
        How should spammers be dealt with ?
        • Ban their original networks
        • Throw them in jail
        • Kill them
        • Fine them 0.01$/email and improve third world infrastructures with the money.
        • Filter/Ignore them.


        I'd personally go for the last option... Maybe the next-to-last if their suit takes place in a really democratic place (there are 278 millions American citizens and 2,2 of them are in jail, this is a *lot*).
        • You make a good argument for killing them rather than throwing them in already overcrowded jails. I'm sure if we killed just a few thousand that most of the rest would get the message and the spam problem would be reduced greatly (something that doesn't happen at all with number 5).
        • I like your last option best, too. I hate to suppress anyone's right to say whatever they want to, but then I want to reserve my right to what I choose to pay attention to.

          Under the existing technology, a spammer is like the royal pest on a city bus which takes advantage of the captive audience. The analogy here is that we have to download our POP box, we have no way of arranging our affairs to where the signals exist, but we deliberately choose not to tap into them.

          I believe the technology must chang

          • by Cato ( 8296 ) on Monday August 11, 2003 @08:32AM (#6664514)
            See http://death2spam.net - this is a commercial mailbox service that appears to have really good bayesian-style spam filtering (referenced by Paul Graham in a recent article) - they even fetch URLs in some messages to filter based on website content. They don't require individuals to train on their own messages, which may be controversial but also makes it feasible to deploy this at large scale in ISPs.

            Without major ISP deployments, the response rates to spam will not go down, since the clued-up individuals who deploy filtering themselves would never have responded to spam anyway.

            Your RF analogy is interesting but it breaks down for people with wireless mobile phone links, dialup when travelling, and so on. The best thing is to make spam unprofitable so it goes away.

        • by felis_panthera ( 160944 ) <felis.panthera@nOSPAM.gmail.com> on Monday August 11, 2003 @11:41AM (#6666058) Homepage
          Out of that 2.2 million people, somewhere near 700,000 [mpp.org] are in jail from possession, use or distribution of marijuana. A law that was originally used to control migrant mexican workers has bogged down the american legal system to the breaking point. Imagine, 700,000 new cells open for child molesters, rapists, spammers, and SCO executives.

          Wouldn't it be grand? [mjlegal.org]

          PS: Sorry about the OT, but things like this need to be said whenever the opportunity presents itself.
    • by ctr2sprt ( 574731 ) on Monday August 11, 2003 @04:29AM (#6663707)
      Spammer: Duck season!
      You: Spammer season!
      Spammer: Duck season!
      You: Duck season!
      Spammer: Spammer season! Fire!
      *bang*
  • by frovingslosh ( 582462 ) on Monday August 11, 2003 @04:12AM (#6663657)
    None of these spam filters will have any effect on spam at all if they are just installed on the systems of people who hate spam and would never buy from a spammer anyway. Hell, they might even have the opposite effect; I will never buy something if I get spam for it. But if I personally filter my spam and don't even see subject lines, I might end up buying the product without knowing they also marketed it by spam.

    Spam is effective because it reaches millions of people who are not installing these filters on their systems. Until ISP's start applying these filters to all spam by default, then the spam filters will have no effect at all, exactly the same number of marks will be reached and respond no matter if the people who know better than to respond to spam go ahead and filter their e-mail or not!

    • Hell, they might even have the opposite effect; I will never buy something if I get spam for it. But if I personally filter my spam and don't even see subject lines, I might end up buying the product without knowing they also marketed it by spam.

      Just stay of herbal Viagra and penis enlargement pills, man! :)

    • by Plug ( 14127 ) on Monday August 11, 2003 @04:20AM (#6663682) Homepage
      Realistically, I don't give a damn how much spam _you_ get, I care that _I_ don't get any.

      You cannot automatically filter spam. Bayesian filtering works because it works on your own personal items only, and you have a method of manually removing false positives. There is nothing worse than the possibility that an ISP will filter out a real email in their spam system. That simple fact makes server side spam filtering impossible for most situations. You can filter spam into /dev/null (unacceptable), you can filter into a spam box (How many POP users would that rule out, who only have one POP box?), or you can keep it bundled in email with a flag, and expect people to update their clients, in which case you have the exact scenario you have now - the client has to do something themselves.

      Until Hotmail et al starts offering bayesian filtering with a separate 'spam' mailbox, consider server side filtering worthless.

      I am smart and don't get any spam. A lot of people I see in my line of work, aren't. These people are going to get something like Outclass [vargonsoft.com] (an Outlook plugin for POPfile), and then they are going to see the problem go away, and they're not going to lose any email in the process.

      I'd rather use SpamBayes, but the Outlook plugin [python.net] has an annoying bug [sourceforge.net] that renders autocompleting addresses in Outlook useless.
      • by frovingslosh ( 582462 ) on Monday August 11, 2003 @04:42AM (#6663748)
        Realistically, I don't give a damn how much spam _you_ get, I care that _I_ don't get any.

        But you still do get spam. Exactly as much of not more because you use Bayesian filtering. Spam still wastes your bandwidth to download that spam before it can be filtered. Spam still wastes any inbox size limits your ISP might impose. Spam cuts into any quota a forwarding service might now or in the future impose on your account, or it could take you to a higher charge level if you pay for a forwarding service. It costs your ISP money, costs that one way or another are eventually paid by you. Even the processing power for that Bayesian filtering costs you CPU cycles, while having no negative effect on the spammers whatsoever.

        While you might not think you care how much spam I get, you might care if dozens, hundreds or thousands of other users at your work also get tons of spam, particularly when all of that spam significantly cuts into your bandwidth. And you will care when overload from spam on your mail server is so bad that it causes failures, effectively causing a D.O.S. situation.

        And as long as geeks happly play with their little Bayesian filters, they stop seeing spam and so stop complaining to the providers that are letting spam get through. They stop doing other things that might make spammer's life difficult. Heck, I fully expect some spam haters with an additude like yours to say within earshot of a congressman or Senator something like "Oh, I never get any Spam. Spam can be filtered easily and nothing should be done about it". The spammers should love Bayesian filtering, it takes the presure off them while allowing them to reach exactly the same number of marks with a mailing.

        • by Plug ( 14127 ) on Monday August 11, 2003 @04:52AM (#6663777) Homepage
          I don't disagree. I think that eventually we should move to a better email model - something like TMDA [tmda.net] perhaps, where there is no guarantee that spammers can reach mailboxes. Or better legislation to make spamming punishable, controls on mail routers on million message mailouts, etc. Or djb's Internet Mail 2000 [cr.yp.to], which moves the onus onto the senders network to store all 1m messages at a time, until people pick them up.

          The other thing you can do is impose a microcost for mailing - at 1c/mail, spamming isn't economical any more. But then that is going to penalise the people who have legitimate reasons to send a million emails at a time - you'd have to have a very good micropayment system working on the Internet to do this.

          However, those things need widespread change, and they need people in positions of power. Joe User at home can push for it, but they still get spam and they still want a short term solution. I suggest that even if they're filtering, the action of having to check their spam filter will make them irate enough. I see it as being like IPV6 - everyone would really have to change at once for the system to be most effective. (I use Freenet6, do you?)

          Now that viruses are public, caught quickly, and Microsoft are being a lot less lax with security (I am in no way commending their effort, but they at least mostly fixed the Outlooks), you don't see people writing them nearly as often. I feel spam will get the same.
          • My ISP provides me ipv6 natively. Yep, a full /48 for me. And it's on a plain vanilla home DSL line.

            Aug 11 03:19:02 traminer pppoe[19276]: Sent PADT
            Aug 11 03:19:02 traminer pppd[12690]: Serial connection established.
            Aug 11 03:19:02 traminer pppd[12690]: Using interface ppp0
            Aug 11 03:19:02 traminer pppd[12690]: Connect: ppp0 <--> /dev/ttyp1
            Aug 11 03:19:08 traminer pppoe[12694]: PADS: Service-Name: ''
            Aug 11 03:19:08 traminer pppoe[12694]: PPP session is 4029
            Aug 11 03:19:12 traminer pppd[12690]: local
        • by schon ( 31600 ) on Monday August 11, 2003 @10:25AM (#6665286)
          spammers should love Bayesian filtering, it takes the presure off them while allowing them to reach exactly the same number of marks with a mailing.

          I'm afraid you've made the cardinal mistake of thinking that spammers follow logic.

          First question: Why do people install filters on their mailboxes?

          Answer: To stop spam.

          Now, take a look at any interview with any spammer.. you'll note that when they're asked, the spammer will say "I don't send it to people who don't want it."

          They'll also say "we're always coming up with ways to bypass filters."

          Now, you'd think that with the two statements, that one of them is false - however (besides the fact that spammers lie), any sociologist will tell you that the spammer actually believes he's telling the truth in each of these statements..

          How he justifies it in his mind is that he believes that even though someone has installed a spam filter, that this person only wants to filter spam from other spammers - that his spam is somehow "special".

          Spammers are sociopaths, and like all sociopaths, they believe the rules do not apply to them.

          If spammers weren't sociopaths, and were capable of applied logic, then they'd realize that any filter (not just Bayseian) would benefit them.. but then, if they weren't sociopaths, they wouldn't be spammers in the first place.
      • by Anonynmous Cow ( 637479 ) on Monday August 11, 2003 @04:46AM (#6663760) Homepage Journal
        Speaking of filtering for others... I don't - but I do run my own little mail server.

        Even after implementing all the postfix uce rules and adding in the RBL's - and using spamassassin... I still saw some spam slipping in...

        So I hacked together a tiny little perl script that monitors my mail log... after any IP address gets more than 3 "554" messages (generated by the RBL's) the source IP gets a lovely little teergrube.

        I waste their resources and prevent them from trying to deliver any other shit that might get through spamassassin...

        Script can be found at here [jasonjordan.com.au] but is only good for postfix/linux/iptables peoples.
    • bleh [slashdot.org]
    • >None of these spam filters will have any effect on spam at all if they are just installed on the systems of people who hate spam and would never buy from a spammer anyway.

      Still, there are plenty of people who hate spam but don't know how to handle it. At our department, quite a few people receive over 30 spams per day and hate it, but no one has installed a spam filter better than the subject/sender filter built-in in their (Windows) mail clients. One has stopped reading e-mail from his university ac

  • Other filters (Score:5, Informative)

    by dtfinch ( 661405 ) * on Monday August 11, 2003 @04:13AM (#6663660) Journal
    I would have liked to see how my favorite bayesian spam filter, K9, would have faired in your comparison, but it failed to meet your first requirement of being cross platform. It's freeware written in C, is about a 60kb-100kb download, depending on if you get it with the self installer, is easy to use, and has a very small memory footprint. Before today it had sorted my email with over 99.8% accuracy, excluding the first couple days of training, and after only a couple weeks of use, though now it's down to 99.7%.

    I have used PopFile in the past on both Windows and Linux, but found K9 to be better suited for environments where Windows is an option. It's very easy to use, having a windowed interface, and it seemed to learn much faster than PopFile did.

    I haven't used SpamBayes. I'll have to give it a shot.
    • SpamPal (Score:3, Informative)

      by UpnAtom ( 551727 )
      I did my own investigation of spam filters about a week ago. I didn't test the actual algorithms, just the features.
      SpamPal with the add-on Bayesian filter (search Google for it) came out top. It works as a proxy and also provides blacklist/whitelist/known Spammer list checking.

  • Spamprobe (Score:5, Informative)

    by 1029 ( 571223 ) on Monday August 11, 2003 @04:14AM (#6663662) Homepage Journal
    The article didn't mention SpamProbe [sourceforge.net]. It is what I use, and it has worked quite well for the past month or so that I've been using it. Perhaps this is just because the author didn't test this spam filter yet, but I like it quite a lot with my current mutt/procmail setup. Take this for what it's worth.
    • Re:Spamprobe (Score:3, Interesting)

      by opk ( 149665 )
      I'll second this. Have been using spamprobe since December. It took longer than a month before it was fully trained. These days it's very good. And the best thing (except once when someone quoted the full body of a spam when complaining about spams on a mailing list): It has never given me a false positive.
    • Re:Spamprobe (Score:3, Insightful)

      by HermanAB ( 661181 )
      Yes, SpamProbe is the best one I tested and I tested most of them. The reason being that it not only counts single words, but also word pairs. It is about 99.5% accurate for me and never gives false positives. My wife uses it in her law office, where I run it on the server - one database for everybody. It works like a charm and doesn't get tripped up with matrimonial fighting mail, which can resemble sleaze mail in many respects...
  • by KU_Fletch ( 678324 ) <bthomas1NO@SPAMku.edu> on Monday August 11, 2003 @04:16AM (#6663666)
    I love spam protection programs. I've been using them for years, but have to switch every couple of months because of the friggen spammers. The people that make the spamming software don't just sit around cackling about how evil they are. They reverse engineer every anti-spam protection out there in an attempt to get around it. While this seems like a good idea (and I will be playing around with these two programs for a while), it's unfortunately only good up to the point when spammers figure a way around it.

    I wish the government would somehow make the practice illegal, but I doubt they'll ever get anything to stick. The far better option at this point is to have a class action suit of server owners (who provide mail accounts) against developers of spamming software and spammers. I've gotten enough warnings from my university to know that bandwidth costs money. By sending millions of spams a year into any one e-mail server, that can account for a serious chunk of bandwidth used at significant cost to the provider. It won't stop spam all together, but it will bankrupt anybody that has been doing it.
    • I use SpamAssassin (which includes Bayesian filtering, though I don't use it) and it works fine - no need to switch away since it's very flexible and lets me write my own rules for new types of spam, or just tinker with the scores.

      http://spamassassin.org/
    • by spongman ( 182339 ) on Monday August 11, 2003 @06:38AM (#6664035)
      I've been using SpamBayes for about 9 months now and I've never had any problem with this 'new kind of spam' you mention. I just don't see it. I don't have to do anything, write any rules, configure anything, it just gets junked. I've never once had any false positives either I get about 30 spams/day, and out of the 8,200+ spams I have in my spambox, less than 100 of those spams are categorized as having less than 90% probability of being spam.
    • They reverse engineer every anti-spam protection out there in an attempt to get around it.

      This is why a real anti-spam legal reform would clearly equate circumvention of an anti-spam filter with circumvention of a password prompt. Both are attempts to crack into someone else's computer without permission -- indeed, against an express prohibition -- and the former ought to carry the same penalties as the latter.

  • Filtering (Score:4, Interesting)

    by rf0 ( 159958 ) <rghf@fsck.me.uk> on Monday August 11, 2003 @04:16AM (#6663670) Homepage
    Taking I get 100+ spams a day I've found that its a goo idea to at least use tagging. For example posting on usernet I use usenet@domain.com with something in my sig saying actualy email is me at domain dot com. Anything sent to usenet is automatically deleted. Doesn't stop the flow by any means but at least I can track where the spam came from.

    If you are feeling clever you can even use addresses that expire after a week. So something like epochseconds@domain.com

    Just my 0.02p

    Rus
    • Re:Filtering (Score:3, Informative)

      by gfody ( 514448 ) *
      you might find this sight [spamgourmet.com] particularly useful. it will let you set up a temporary address based on a naming convention that forwards to your real address but expires after a few emails. you can setup something like rusxxxxx@asdf.com where xxxx is whatever you want and it will fwd to your real address so if the badguys get your email its no big deal the temp addy will just stop working.
    • If you are going to delete everything that comes to via the Usenet address why do you include a valid email in as your return address?

      you could reduce the flow to 0 by putting

      From: not_real@naimod.moc

      and to be honest if I was an email harvester I might have noticed "user at domain dot com" and be harvesting those too

      • by Anonymous Coward on Monday August 11, 2003 @06:20AM (#6663992)
        Very good.

        Speaking from experience, I know for a fact that many of the harvesting programs (written in perl, running on linux, written by geeks) are very robust at deciphering most email obfuscation methods. You all sit and shake your fists, and the spamware writers are laughing their asses off.

        You have the easy answer: don't obfuscate your email, don't even bother putting it on your posts.

  • Missing the point? (Score:5, Insightful)

    by aquishix ( 684586 ) <aquishix@NOspaM.dartmouth.edu> on Monday August 11, 2003 @04:17AM (#6663672)
    As someone who recently acquired a B.S. in mathematics several days ago, I understand how these filters work. They are an excellent way to fight spam over the older methods.

    However, I think that ultimately this sort of thing misses the point. Spam needs to be fought in the courts, not in the battlefield. I'm afraid that the success of these filters will cause spam NOT to become illegal, and thus lead to a world where we have a constant trickle of spam, albeit in small amounts.

    I think we all agree that we want spam to be gone entirely, as is evidence by the first post being labeled as "troll" ;)
  • I have been using POPFile since January, and I know it uses pseudowords for all kinds of features spammers use, like comments, remote images etc. (html:comment, html:imgremotesrc).

    Does SpamBayes do anything similar?
    • Yes it does, the developers have created a test suite and a very extensive tokenizer. Any additional pseudowords, or new ideas to tokenize a message are tested very throughly before they are added (as most tend to actually lower accuracy instead of raise it). There have even been tests using SpamBayes on just headers and just message bodies and both have worked very well.
  • by Tehrasha ( 624164 ) on Monday August 11, 2003 @04:23AM (#6663691) Homepage
    ...they only prevent you from seeing it.

    Your server and its harddrives still end up being a storage bin for it, and the spammers will continue to send as long as your machine allows it to be recieved. Always remember that spam differs from postal junk mail, in that the -receiver- pays for it. Unsolicited postage due mail.

    Spam must be -blocked- and the ISPs that allow/encourage its continued spread must re-educated, or be put out of business. Only when spam becomes costly to send with it diminish.

    The current proposed laws concerning the subject are currently focusing on content rather than consent. They dont mind if you get spammed with hundreds of ads, provided what is being advertised isnt fraudulent. They overlook the fact that the claim of you having 'opt in' for the spam is in itself the lie and fraud.

    --Teh

    • Both filtering and blocking help. Blocking helps by not even letting the mail enter your server, and filtering helps by not showing you the mail even if you receive it. If you can't see it, you can't buy anything from the spammer (well, at least directly because of the spam). And I'd say the biggest cost of spam is wasted hours spent looking at the spam when you're checking your mail.
  • by Peter Cooper ( 660482 ) on Monday August 11, 2003 @04:24AM (#6663693) Homepage Journal
    I have long been an advocate of Bayesian or keyword based spam filters, but have recently been forced to change my outlook, and to argue that MULTIPLE SIMULTANEOUS solutions are the answer.

    I encountered a very simple but unique spam system which works entirely on the sender's address. Simply, you create a small database with the domains/addresses you want to whitelist. Then, a program screens your mail, and if the sender is not in your whitelist, it sends an e-mail BACK to the sender with a simple URL (or even an actual link for HTML e-mail clients) which states that they REALLY want to send the e-mail to its destination. When this is done, they are added to the whitelist. Therefore, mails from forged remote addresses are no longer a problem, and neither are mails from trusted sources. And, better than SPEWS or similar blacklists, the sender gets a SECOND CHANCE to send their mail to you.

    There's a commercial solution using this system right now, although the URL escapes me.

    Of course, one could encounter problems when ordering online, say. Droids at Amazon will not be clicking your links to make sure your order receipt got through. One could argue that you'd put things like Amazon.com in the whitelist, but what if someone used amazon.com as a spoofed e-mail domain/address? Ay, there's the rub. But if this system were tied in with a Bayesian system, it'd be pretty unbeatable. What's more the Bayesian system would have extra data for negative matches, in the form of e-mails that were never 'approved', and positive data in the form of those that were.

    So, I'd be more interested in producing a homebrew system that used MULTIPLE weaker systems, than one supposed 'sure fire' method.. as I feel no one method is perfect, whereas multiple systems can approach this nirvana.
    • by ctr2sprt ( 574731 ) on Monday August 11, 2003 @04:38AM (#6663732)
      Any approach that triggers an automatic action on your behalf is bad, because it can be turned against you. It's not likely that email would make a terribly good DDoS service, but a system like the one you describe would certainly be vulnerable to it. And I think it would only last a week, at most, before spammers figured out a way around it. They can already handle "NOSPAM" being inserted in email addresses, and recently added the ability to reverse and combine email addresses until they get something plausible.

      I do agree with you that we need multiple layers of safeguards in order to solve spam - or at least to hide it away so nobody has to look at it - but I don't think your specific example is very good.

    • on the linux side you can just use tmda.net for challenge response.
    • by scj ( 97603 ) on Monday August 11, 2003 @06:38AM (#6664036)
      I had thought of something similar for fighting spam. Here's how I'd handle each email:
      1. If the email is from someone in my whitelist, allow the mail to go through and feed it as 'ham' to the Bayesian filter.
      2. If the email is not in my whitelist, run it through spam filtering software (Spamassassin [spamassassin.org] works well) to determine if it is likely to be spam.
      3. If it seems like spam, then use a challenge-response system (like TMDA [tmda.net]) to find out if a human sent the email.
      4. If the mail doesn't seem like spam, just deliver it. If I get 3 non-spammy messages from the same person (separated by a day or more) then add them to my whitelist automatically.
      5. If someone responds to the TMDA challenge, put them in the whitelist and deliver the original email.
      6. If no one responds to the TMDA challenge after a week, feed the mail as 'spam' the the Bayesian filter.
      In addition, I'd use a system like Sneakemail [sneakemail.com] to generate random email addresses to give out to businesses I want to do business with and use to sign up to mailing lists. These email addresses would be added to my whitelist so they could send me mail without going through the challenge-response system. If they start spamming me, I put the random email I gave them on my blacklist.

      This system has the following benefits:
      • Business mail I want (like receipts and newsletters from companies I do business with) get through always since the Sneakemail-type address is whitelisted. This solves the problem of businesses not responding to TMDA challenges.
      • My real email address is protected from businesses who are likely to sell it and from people farming addresses from mailing lists.
      • Personal email that the spam filter sees as non-spam gets delivered without bothering the sender with a challenge-response system.
      • Personal email that does seem spammy by the filter still has a second chance to make it through the system with the challenge-response system. This should reduce false-positives to include only spammy emails from people who don't respond the the challenge.
      • The Bayesian filter is automatically trained based on mails from people in my whitelist and mails from people who never respond to the challenge-response.
      You would still get spam with this system (personal email that your filter thinks is non-spam), but hopefully your false-positive rate would be zero. Also, you don't annoy other people much by only sending challenge-response messages to spam-like emails. Finally, this would be easy for end users to use. They don't have to train the spam filter, since it should train itself. The only complicated part would be generating and using the random emails that you give to businesses and mailing lists.
    • ...it sends an e-mail BACK to the sender with a simple URL...
      And, not being on their whitelist, their email filter sends you an email back with a simple URL...
  • "Bayesian" (Score:4, Insightful)

    by RDPIII ( 586736 ) on Monday August 11, 2003 @04:40AM (#6663740) Journal
    I don't mean to troll, but I hope it's not too late to put an end to the unfortunate term "Bayesian spam filtering". This is perhaps the worst abuse of the adjective "Bayesian" I've seen, because nothing crucially depends on the application of Bayes' Theorem and/or on the use of Bayesian methods (informative priors, model selection, etc.). Why not simply call it "data driven spam classification" (as opposed to "rule based") or "empirical spam filtering"?

    If the spam disaster had struck fifteen years ago, we'd all be talking about "neural spam filtering" (using artificial neural networks, ANNs) and basking in the warm fuzzy feeling imparted by the term "neural". But ANNs and Bayesian classifiers have the same interface: both are trained on labeled data and can be used to classify unlabeled data. The implementation details are not of primary importance, and if you think they are, I'd encourage you to look into large margin classifiers instead of Naive Bayes or ANNs.
    • Re:"Bayesian" (Score:5, Informative)

      by file-exists-p ( 681756 ) on Monday August 11, 2003 @05:58AM (#6663941)
      As far as I know, many of those filters are based on a decision rule of the form

      P(mail is spam | words X, Y, Z, ... are in it) > 1-epsilon

      The computation is then done using Bayse's rule (P(A|B)=P(B|A)*P(A)/P(B)) under certain independance assumption which makes it tractable.

      So this is actually bayesian filtering ...

      My favorite filter is spamoracle [inria.fr]
  • wtf (Score:2, Insightful)

    by timerider ( 14785 )
    When will 'the net community' finally get it?
    filtering is no solution as long as there's no way to stop the spammers!

    Or would you say that ignoring the corpses in the gutters would be a solution to the problem of violence on the streets?

    bye
    [L]
    • When you could get a fence setup in the streets, with the violent people on one side and the remainder on the other, that would be a solution.

      This can be compared to filtering.

      Of course it is better to get rid of the problem, but just as with violence this is not realistic.
      No matter how many laws, there will always be people or countries who just don't care.
    • Re:wtf (Score:3, Funny)

      by Chokma ( 610031 )

      filtering is no solution as long as there's no way to stop the spammers!
      Or would you say that ignoring the corpses in the gutters would be a solution to the problem of violence on the streets?

      Your analogy is slightly flawed. In the case of spam, it would be correct if:

      • I would have to examine every corpse closely to determine if it is sill alive
      • I would have to manually remove the corpse from the street

      On my system, SpamAssassin kills 99% of the Spam, carries it outside, buries the remains in the sp

  • By this article, SpamBayes.

    Which only works out of the box with Outlook 2000/Express. Woopy doo.

    Are there any recommendations for those of us who aren't forced to use outlook? I use Eudora my self, have been for years, thus I'm not looking for a new email client recommendation. ;)
    • by Gaza ( 3339 )
      SpamBayes has a very well done pop3 proxy that will work with ANY pop3 mail client, including Eudora. There is also an IMAP filter for those that like IMAP and for those procmail fans it also has an app called hammiefilter which is a command line version of the SpamBayes tools.

      SpamBayes also has a very well done and integrated Outlook plugin which leads to the common misconception that SpamBayes will only work with Outlook.

      Also note the review mentioned that both SpamBayes and POPFile work on multiple pl
  • YFI list (Score:2, Informative)

    by usotsuki ( 530037 )
    1. E-mail contains HTML tags of any sort, except for <A>
    2. E-mail contains attachments (unless solicited; whitelist)
    3. With all non-alphanumeric characters removed, certain case-insensitive keyword matches can detect spam
    4. E-mail is a forward or looks like chainmail / Nigerian scam
    5. E-mail contains junk strings in subject or sender
    6. E-mail comes from you, but header doesn't match your send name
    7. E-mail is excessively large (>20K) and unsolicited (whitelist)
    8. E-mail headers and/or text contain Mojibake, if unsolicite
    • Re:YFI list (Score:2, Informative)

      by Oddly_Drac ( 625066 )
      "Address doesn't match reverse lookup"

      You'd be surprised how many DNS servers are completely misconfigured for this, but I think that a simple ping to the address given could actually show if it _existed_.

      Personally I've found that I can reduce my spam by a huge amount by never viewing HTML...which brings a thought about tracking and tracing the webbugs in any given piece of HTML email...

    • Re:YFI list (Score:2, Interesting)

      by aduxorth ( 450321 )
      another goodone is if the domain from the envelope sender doesn't have a MX record. bam guarenteed spam. The other one is to verify the sender not just the domain. This kills all those spams from lkiqprejbn@yahoo.com which are obviously bulldust.

      That alone kills off about 70% (IMO) of the spam that comes through servers that I administer, and as far as I know, only 2 emails(over the last 4 years or so) that wern't ment to be rejected were rejected because they had invalid sender envelopes.

      HTH
      cya
      Andrew
  • Sorry, but filters are not the final answer. Even when the filters can "learn", the user still has to expend a certain amount of effort to "teach" the software. And quite frankly, spammers (or the people who write automated spamming software) just need to study the filters and learn to get around them. And worse, you can never be sure that the filter is not deleting email that you actually want, unless you set it to never delete suspect mail, allowing you to examine and delete it manually. But at this p
    • by frovingslosh ( 582462 ) on Monday August 11, 2003 @05:33AM (#6663879)
      The only thing that can truly save email is to switch to a service that requires authentication of senders.

      I agree with everything that you said about filters being ineffective. But I strongly disagree with your "only thing" statement. Particularly if you mean it as any of the systems I've ever heard about, such as "If it's not in the address book, the sender must acknowledge a challange message" type of approaches. The problem with such systems is that many of us get quite a bit of e-mail each day from people who are not in our regular address books, some of it quite important to us. We do not want that mail lost because the system at the other end was not in out address book and did not waste their time responding to a challange and response type system. For example, say I purchased something on-line from a vendor I had never dealt with before. Their e-mail system may automatically kick out an e-mail that informs me the product was shipped and give me an important Fed-ex or UPS tracking number. I'm glad they do such things with their shipping systems, and I don't expect them to manually respond to every challange they get back; realistically they will send any such challanges to the bit bucket and people who want e-mail that is important to them will end up never getting it.

      So I do not believe that Authentication of senders , at least in any of the traditionally suggested ways, is the correct approach. Much of the spam problem we have is due to what I consider flaws in SMTP. I would very much like to see a replacement for SMTP that considered the spam problems (as well as other problems inherent in SMTP). As an example, another post here mentioned a system where the mail is held, not on your ISP or upstream provider's system until you download it, but rather is held on the sender's or sender's ISP's system. The recipent would presumably receive only a very short indicator of where they have mail waiting, and would fetch it themselves when they are ready to receive it. The puts the burden of storage on the sender or the service provider for the sender, and avoids considerable bandwidth wasted by senders who supposedly send out e-mail with addresses generated to match all combinations of up to x characters (the excuse Mindspring gave to me when addresses that I created but never gave out or used started getting spam, not that I believe them). In addition to putting this burden on the sender, it would insure that there was a good address in the e-mail to fetch the mail from, so spammers would have a much harder time injecting their spam into the system and would be much more traceable. And while I'm not foolish enough to think that laws could completely stop spam, we've seen how laws did drastically curtail fax spam, and some fax spammers have recently been made to pay serious fines. I do think laws would have a big effect on spammers; ther are a lot of spammers who just don't want to have to move out of the country to keep up spamming, and those of us who hate spam will track the spam back to US sources if we have a law with teeth in it to impose fines (or worse) on them when we do.

      Of course, and change to or replacement of SMTP must be phased in over time. It's not a short term solution to spam. But I expect SMTP would quickly go the way of gopher or archie or the rest if a viable new protocol was presented that addressed these problems effectively, and this is where I think out greatest chances for sucess are.

      • say I purchased something on-line from a vendor I had never dealt with before. Their e-mail system may automatically kick out an e-mail

        Using TMDA [tmda.net], you would generate a "keyword" address: A unique addressed, identified by a keyword embedded in the address, which would allow your vendor to bypass the C/R system. If they keyword address starts being abused then (1) you can easily disable it, and (2) you know not to do business with that vendor again.

        As an example, another post here mentioned a system w
  • by Anonymous Coward on Monday August 11, 2003 @05:03AM (#6663799)
    I know this is slightly off topic, but can someone answer me a reasonably simple question thats been bugging me for a while?

    Why not instead of hunting down the spammers do we not hunt down the people who are selling and advertising their junk via the spammers?

    The spammers purposly make themselves difficult to find, but it must be easier to track down a company that is collecting money and sending out products? Why not make the using of spammers services illegal and fine and punish those doing so?

    I think Im correct in saying and please tell me if Im wrong, but here in the UK a similar situation is people "fly-posting". In these cases, if advertising posters are put somewhere illegal or unwanted, it is not the person who put the poster up that is fined, but the club, record label, whoever is beign advertised that takes the rap.

    Just my 0.02p
  • by Zog The Undeniable ( 632031 ) on Monday August 11, 2003 @05:15AM (#6663836)
    Moz's Bayesian filtering works well, but its Achilles heel is that it doesn't work on the POP3 server, so you still have to download everything. As POP3 allows the header and the first part of the message body to be read without downloading it, surely there could be an option - once Moz has been trained and you're fairly sure the false positive rate is negligible - for filters to operate on the server and delete spam from there?
    • by pe1chl ( 90186 ) on Monday August 11, 2003 @05:46AM (#6663906)
      It would be nice if there was filtering done on the server. Then you would not need the packages that are reviewed here.

      However, that means a change to the server, and a change to the POP3 protocol. The ISP would have to install a filtering plugin or a modified version of the server, and the client would subscribe to this service and train it (every client would have his own dictionary). With the first few messages there would be some special POP3 report back to the server indicating that you consider it spam, and from then on the server would filter on its own.

      However, that would be difficult/impractical to roll out, so you will have to live with clientside filtering like in Mozilla.
  • In related news (Score:4, Informative)

    by heli0 ( 659560 ) on Monday August 11, 2003 @05:44AM (#6663899)
    If you have ever signed up with the Direct Marketing Association's Mail Preference Service (list of people not to send junk mail to), but continue to receive stacks of crap every day, here is what you can do about it: Prohibitory Order [mcgladrey-family.us]

    Links to pdf's you need to print and mail in included.

    "A little-known Federal law allows individuals to send a Prohibitory Order against companies that are sending unsolicited sexually provocative or erotically arousing mail. The Supreme Court went one step further, allowing individuals to decide what constitutes "erotically arousing" mail. The law makes it illegal for a company to send mail to an individual within thirty days of receiving the Order."

    "Postmasters may not refuse to accept a Form 1500 because the advertisment in question does not appear to be sexually oriented. Only the addressee may make that determination."
  • Everyone? (Score:2, Insightful)

    by Jon Peterson ( 1443 )
    "Support both Windows and Linux " ...
    "The first requirement is because I wanted the results to be applicable to everyone"

    My how the definition of everyone has changed. So it's bad luck Mac, Solaris, *BSD, HP-UX, VMS users...

  • by CGP314 ( 672613 ) <CGP@ColinGregor y P a lmer.net> on Monday August 11, 2003 @05:49AM (#6663919) Homepage
    One of the things I love about popfile is it is not a Spam filter. It is a general mail filter. I have about ten categories of mail that it sorts out for me. This also helps cut out false positives. 'Work', 'Personal', 'Friends' and all much more similar to eacth other than 'Spam'.

  • by nuwayser ( 168008 ) <pete&tux,org> on Monday August 11, 2003 @06:16AM (#6663987) Homepage Journal
    An analysis of filtering methods against spam is kind of like a comparison of bullet-proof vests in that there's no incentive to stop someone from pointing a gun at you and firing it. In the past, spammers have been grossly affected by more sweeping changes, and I'm afraid filtering methods are only creating the mindset of, "Give up, use this software, it will do the deleting for you." It takes the attitude of, "just delete the stuff" and makes it automatic; sure it's convenient for a time, but in a year you're still going to get spam and your ISP will likely have fewer resources to deal with the complaints.

    I'm saying, why not focus instead on technology which puts a bigger dent in spammers' ability to operate, like how to secure against proxy hijacking [uoregon.edu].
  • by rediguana ( 104664 ) on Monday August 11, 2003 @07:20AM (#6664182)
    POPFiles utility does not lie just in managing the spam menace. To me, the real utility in POPFile is the ability to create x number of buckets and train it to sort your mail. SpamBayes looks great for spam but has no further utility. I like having POPFile sort my work from personal emails, and file all my mailing lists in another, and even jokes. Of course there is the spam folder that I check every now and then. I look forward to it being able to support IMAP servers as well.
    • I agree, I just discovered POPFile last week when it was shown on BBSpot. I use an exchange plugin called Outcast that allows POPFile to work over exchange also. I have several buckets setup to help sort incomming email into the correct folder for different projects and it works fantasticly. I've only been training it for about 3 days and it already sorts with almost perfect accuracy.

      POPFile, and Outcast rock.
      • I installed POPFile on my parents computers; I was worried because I thought the interface (web interface) would be confusing to them; since you couldn't do everything within the email client itself.

        Works great. My father, who gets far more spam than the average person (why I don't know) has virtually 100% success rate.

  • by setien ( 559766 ) on Monday August 11, 2003 @09:24AM (#6664822)
    No it's not.
    I get spam at the rate of 1 spam mail per 6 months or so. Or maybe even less. I can't remember getting a single spam email on my actual email address for about a year.

    If you have an account on a crapless domain (i.e. not hotmail.com, msn.com, aol.com and the likes),
    it all comes down to this very simple rule:
    Do not, under any circumstance, have your email address posted publicly accessible ANYWHERE on the web.
    It WILL get trawled. And then it will be spammed relentlessly.

    If you have an existing address you don't want to give up, or an address at hotmail.com or a similar place, dump it.
    Then exercise a bit of common sense about where you use your actual address.

    I have a domain which catches email to unknown addresses and put them in my regular mailbox.
    Whenever I have to give an email address to some place on the web, I use *domain-i-am-currently-visiting*@mydomain.com. So if I am visiting foobar.com, I would put in foorbar.com@mydomain.com.
    I have been doing this for years. It enables me to see what was the source of the leak when I get spam on one of the addresses.
    It has taught me one thing: I have never, ever, ever, in all my years of online shopping, forum posting etc, come across a single website that have ignored their own privacy statement. Ever. Even the slightly sketchy sites (like divx subtitle sites) don't leak addresses.
    I was surprised to realize this.

    The only addresses I ever get spam on are the ones I know to be publicly displayed on the web.

    So it's that easy to avoid spam.
  • by momus_radar ( 668448 ) on Monday August 11, 2003 @10:13AM (#6665169)
    This method of combating SPAM is amazing to me. Admitingly I'm a little behind the geek times so my interest in this method was peaked when Apple released Mail.app. But I still use Mac OS 9 and am in no rush to run X yet so I'm glad to see there are alternatives that I can use.

    I think the only reasonable way to rid the world of SPAM is to get the foolish folk who respond to it to stop. The reason there is so much of it now is that it seems to work; there are people who actually respond to it. If these people stopped responding to it the use of SPAM would most likely diminish.

    Sending SPAM costs money. No sence spending that money if no profit is made.
  • by Moryath ( 553296 ) on Monday August 11, 2003 @10:56AM (#6665537)
    The "unsure" feature directly combats the latest Spammer technique -- filter poisoning.

    You've all seen it work; the Spammers don't just send you the same spam once, they send you it 5 to 20 times, and they include a clipping from the headlines or something under their pitch.

    They're not doing it to get that one mail past to you. They're actually HOPING that you classify all 20 mails as spam.

    Why?

    Because every time you classify that mail as spam, EVERY SINGLE WORD of that news clipping is "poisoned" inside the filter, and becomes an indicator of a spam. Then you turn around, and get an email from someone legitimate using those common words... and it gets wrongly classified too.

    Enough false positives, and the spammers win, because they'll get you to turn the filter back off.

    Enough is enough -- time to establish open hunting season on Spammers.
  • by Cytotoxic ( 245301 ) on Monday August 11, 2003 @11:37AM (#6666018)
    As a network/web/computer manager, my email has been provided to dozens of companies and trade shows. I still remember the day (August, 3 years ago) when someone first sold my address to a spam list. I went from 2-3 spams per day to 15-20. This spring brought another explosion, this time into the 100+ range. I am currently receiving over 6,000 spam messages every month! Obviously my main email address was useless and needed to be burned on a pyre to purge the evil.
    After a week or two of this, I installed SpamBayes in the form of it's outlook plugin. I showed it my email archive as my "good" messages, and a bunch of spam gleaned from my deleted folder as "bad". My mailbox is now perfectly clean. I have received at least 15,000 spam messages since installing SpamBayes, and I have probably had to hit the "Delete As Spam" button about 10 times for ones that it missed, most of those being variations on the Nigerian scheme. It has never grabbed a real message, and the "Unsure" feature localizes everything that I really need to look at in one place.
    If you have a spam problem, get SpamBayes. It is that simple. There is no need to speculate about that better method that you thought up, or how it really won't work because of XYZ theory... it works almost perfectly, and it lets you know about anything that it is not sure about with the "Unsure" folder, so it never throws the baby out with the bathwater. In short, this is almost the perfect Spam filter. It even caught the emails that were using GIFs to avoid being filtered on content, placing them in unsure until I said "this is spam", after which I never saw another one. Pretty darned cool!
    It is actually kind of fun to watch this thing work. I came in this morning to find 568 new messages in my spam folder, 3 in unsure, all of which were spam. No spam anywhere to be found in my inbox, just 15 unread messages that were correctly left alone by SpamBayes. Just imagine having to flip through 600 emails to find 15 real messages! Now I just hit "CTRL-A DEL" in my spam folder and it is all gone! 5 seconds a day to deal with spam, I can live with that....
  • by wytcld ( 179112 ) on Monday August 11, 2003 @11:58AM (#6666202) Homepage
    SpamAssassin has Bayesian learning, which I have running but not for long enough to test. I recently set up MIMEDefang as a Sendmail milter calling SpamAssassin (which calls Razor). This setup allows Sendmail to reject e-mail beyond an arbitrary SpamAssassin score. The remote mail daemon is informed the mail cannot be delivered.

    Setting that score at 8 has resulted in no false positives over a week (I log From and Subject information - it's all obvious spam). Then stuff that scores between 5 and 8 I divert to a separate mail box, which I comb through every day or two. There have been two false positives that ended up in that over the week. This is with hundreds of e-mails for a half-dozen users coming in a day. I also end up, with this setup, with 2-4 spams making it through to my own mailbox (the bussiest on the system). These are, because of the filtering, the least obnoxious, and easily enough report to Razor to spare others. Meanwhile, I like to keep a window open to the mail server running "tail -f mail.info | grep REJECT" and watch a dozen or so attempted spams an hour refused acceptance with a message like "554 5.7.1 SpamAssassin score of 15, rejected" back to the origin, which is enough that if it wasn't spam any good mail daemon will inform the sender, and they can find another way to get through.

    Even if this gives spammers a clue about ducking SpamAssassin, the spams that can get by it are by far the least obnoxious. I look forward to seeing if the Bayesian feature helps (it feeds itself anything ti scores at over 15 by default). But it's a pretty good system short of that. If it became standard for ISPs to reject all mail with a SpamAssassin score of 8 or higher, the loss of legitimate communications would be exceedingly rare, and politeness standards would be encouraged.

I tell them to turn to the study of mathematics, for it is only there that they might escape the lusts of the flesh. -- Thomas Mann, "The Magic Mountain"

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