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Spam Solutions from an Expert
Mod N writes "SecurityFocus has posted a nice survey of anti-spam technologies by spam expert Neal Krawetz, in which he delves deeply into the specifics and pitfalls of the numerous proposed solutions. Krawetz makes it obvious that securing the email infrastructure is a very complex problem that many of the current (simple) solutions can't solve alone."
Excuse me, what? Where's the proof? That's quite a brave statement to be making considering i've never seen this cracked, ever.
I challenge someone to find an automated response to C/R.
I did hear of a theory where C/R was being cracked by taking the C/R image, posting to a porn session, and letting a seeing person do the work. However, i've yet to witness this in practice. Show me the automated response to C/R that exists beyond a blog theory, and i'll believe. Until them, i hardly consider it "marketing hype".
The truth is 90% of spam comes from open relays, that is SMTP servers that can be tricked (a bit like lying to a 5 year old) into accepting and sending out massive ammounts of mail. Simply blocking open relays using The Open Relay Database at http://www.ordb.org/ or other open relay checking utility will save you lots of time if you run your own mailserver. When we can bascially negate the usefulness of open relays to spammers, they will then have to rely on their own bandwidth for the most part providing they cannot comprimise other "closed" relays.
I am in full support of using the broad-powered, freedom crushing Patriot Act in apprehending and imprisoning spammers. We might as well get some good out of it.
My free anonymous (as in they can only be traced back to a common e-mail account on my server) e-mailer uses a simple quiz to keep spammers out.
The form page records the IP address of the visitor along the with the question number they were given in a file named with the IP address. That number is never sent to the client. When they hit submit the file of their IP is opened, the question number is read in and the answer given by the user is compared to the stored answer. The file is then deleted and if the answer was correct the e-mail is sent. Otherwise it's not.
This forces my custom form to be used to be able to send the e-mails. And it's not possible to simply keep refreshing the submit page to keep sending the message.
And the challenge is in the form of old riddles and a couple new ones like "what's your favorite color?"
Things a bot would never get but that anyone who knows how to use Google can. Someone would have to program a custom bot with the answers in order to even attempt to spam. And even then since everything goes through my mail server nobody is going to sneak garbage past me for long and I know who your ISP is.
I also include a disclaimer with every e-mail. It'd be quite silly for me not to.
Ben
Work Safe Porn
Well, at the risk of sounding like a broken record, SMTP itself is the problem -- it's badly broken, security-wise, and needs to be fixed. It's going to be painful to move to a new mail standard, or to change SMTP so that it's not broken, but that's what needs to happen to stop spam. Thankfully, our friends the Russian Mafia and the ever-growing number of Windows zombie machines are making spam levels so great that, sometime soon, spam will represent such a large percentage of e-mail traffic that fixing SMTP will be necessary, not just something mail admins like myself wish for.
BTW, does anybody have a good figure on what percentage of all e-mail spam represents these days? I'm talking about *all* traffic, too, not just what ends up in peoples' Inboxes after all the filtering going on out there has done its job.
How To Get Humans To Mars
I am not recommending mailblocks, I belive there is a sourceforge project called TMDA which does the same thing. Having said that, my experience comes from using mailblocks:
...
-cr deadlock: This does not exist because when you e-mail someone in a challenge and response system, it automatically assumes they are friendly. So if they have a challenge and response system, it will make it into your inbox, because you e-mailed them first
-automated systems He is correct here. Personally I hate when friends submit my e-mail to third parties without my consent so I do not mind missing these e-mails. I have caught a few while searching my pending folder, and inform my friends I rather have them e-mail me directly.
-interpretation challenge I believe he is wrong here because of a fundamental issue. When dealing with spam filters, the onus of working out refinements is left to the spamee, to make sure they filter out all spam. If a spammer adds a new technique, they get around the filter. With challenge systems, you have a few methods waiting as backup. When a spammer finally figures out how to read your words through AI, you simply change the challenge system and they are back to square 1 in trying to figure out how to defeat. As long as you have a few methods waiting in the wings, the spammers can easily be defeated, and have huge amounts of work to do.
if you doubt this, write an AI system to defeat hotmails gifs. Now what if the next day instead of showing a word, they show you a picture of 3 fire trucks and 2 police cars and ask you how many police cars are in the picture, etc
-Nuke the moon
Was out to lunch with three colleagues today and the subject of anti-spam measures came up.
I managed to appall the one from Berkeley by suggesting that the most practical solution was probably a moderate-size bomb.
B-)
But seriously:
In an arms race, weapons eventually defeat armor. Spam will continue until two real-world things are BOTH brought to bear on spammers:
- Economics
- Muscle
If a governmental solution applying both is not forthcoming soon, I predict that there WILL be vigilantism.
In fact we're already seeing it.
For instance: Subscribing the Detroit area spammer and his lawyer to enough real-world junkmail lists to bury his bills and other US Main correspondence in several daily truckloads of catalogues and other solicitations.
Soon to come: Retaliatory information-war software directed at DDoSer / spammer zombi-net machines. (As discussed in a recent Slashdot article.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
As stated in the article's summary, the main problem with most spam-filter is the need for constant maintenance. We need a solution that requires ZERO maintenance by the joe-users, and yet cost-effective enough to implement.
My ISP seems to have a so-called "Watch Dog" spam filter, where they actually hire people to read spams and filter them manually, that's probably the most effective way to filter spam, but I wonder if it is cost-effective though.
Prior to this October, telemarketing calls were a national scourge. Amazingly, since we signed up for the Do-Not-Call list, we've only received 2 illegal calls. I'm rather surprised, in fact, at the relatively uniform acquiescing to this law. While spam, coming from all corners of the earth and is more anonymous, will be harder to enforce, some law with real teeth may be a good start.
The only thing that will work in the end is some sort of distributed reputation management system. To a certain extent that is what RBLs do, except they are on or off. SpamAssassin does offer shades of grey to the RBLs (differening weights to each one).
To a certain extent this is what we already do in real life. We 'judge a book by its cover' as a first pass (for example people will often walk past a beggar in the street completely ignoring them) and then include other factors. How polite they appear, where they are from, recommendations from friends etc
All other mechanisms suffer from a determined spammer being able to get around them as the article pointed out. Any mechanism that prevents some spammers makes things more lucrative for the rest.