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The Next Step in Fighting Spam: Greylisting
Evan Harris writes "I've just published a paper on a new and unique spam blocking method called "Greylisting". The best thing about it other than achieving better than 97% effectiveness in blocking spam, is that it practically eliminates the main problem of other solutions: the false-positive. There's even source code for an example implementation written as a perl filter for sendmail, along with instructions for installing, so you can get up and running quickly."
I'm going to try to say this as nicely as possible and without trolling:
You have just rendered Greylisting pretty useless by making it open source. Spammers are much smarter than you think and what you have basically done is shown them what they need to do in order to get around Greylisting. That's just my take on the issue, maybe I'm wrong but I doubt it.
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I like the idea though. Since SMTP is broken anyway, why not use another of it's features in a new way to help filter unwanted email. Keep up the good work!
This isn't very reassuring:
"it practically eliminates the main problem of other solutions: the false-positive."
What does 'practically eliminates' mean? If it gives false positives at all, it is just as useless as all those 'other solutions'.
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Time critical mailing will go out the window. I can see how this might make any corporate user irate. The same thing goes for challenge-response, the time delay in the business world is unacceptable.
This would be great for personal mail, but that's about it. ISPs would have the same problems with it because their business-class users most likely use the same servers as their consumer-class users.
If they can get around it by looking at the source, then something was wrong with it, waiting to be exploited. Might as well fix it.
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with all of these solutions to spam..and all of the spam now flooding mail servers...
isn't it time to change the specification (RFC) and possibly the manner in which our current system works? i haven't come up with anything yet, but surely there must be some sort of handshaking/secure type connection that could be used - - some sort of postage (free) that is encrypted into the mail, that states that it is genuine....kind of like the hologram on those windows cds...
i dunno. file this story under redundant.
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I thought it was generally understood that most spam was sent by abusing open relays, thus hiding it's origin. This could be wrong. However if it's not, those figures aren't appllicable. Nor is spam going to be diverted since an open relay is generally running a regular mta and will attempt a retry. For instance, if qmail were running on an open relay and was abused by a spammer it would try again and again with an increasing delay (calculated logarithmically if memory serves) between attempts. So the mail will still get through.
When you further consider that if a spammer hits an open relay and hammers your mailserver from it and all of the "triplet's" are new, you're increasing your traffic, because all of that mail will be attempted again.
I parse the content before I read it (isn't php great? :-)
.exe attachments, any email with the words viagra or penis (or some other words in my list, like "second mortgage" when I don't own a home,) in it gets purged as soon as I pull it off the server.
Any email with HTML in it, any email with
It never gets to my mail program.
I could also filter on subject lines containing any word whi isn't in thdictionary but since some of my friends don't spell too well...
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Question about this system: if it sends a temporary unavailable message or whatever it does, does it log the original message? Where I'm going with this is what happens if a legitimate message is blocked but never resent? Most anti-spam software allows you to view the spam folder, or something equivalet, to check for false positives. How are false positives handled here?
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The article also doesn't measure the amount of spam coming through those relays. Even if there are only 10 open relays in the UK at any one time, it still might be possible for all of the spam to be coming through them.
Certainly, closing down open relays is a good thing, but lowering the percentage of open relays doesn't prove anything about the source of spam
Look at it this way: you can stop crank calls by unlisting your phone numbers. But you can't unlist the hospital, the ambulance service, the fire department, etc.
We're not all end-users. Some of us are the plumbers.
I'm wondering how I'm going to explain that to a new customer over the phone who says "I'll just email that file right now so we can go over it together".
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It deals with spam at the server level. All the wonderful user-level solutions don't do jack to stop spam from being sent. Look at the numbers the spammers show for return rate, and look at how fast spam programs can go, and you'll see that the only solutions that will work are those that make it expensive to send spam. Anything else will just make the spammers send more spam to try and get the hit rate they need.
During the initial testing of Greylisting, it was observed that the vast majority of spam appears to be sent from applications designed specifically for spamming. These applications appear to adopt the "fire-and-forget" methodology.
Spam guards and spam co-evolve. Since greylisting is easy to get around by spammers, if it becomes widespread, spammers will take measures to avoid it, and the net result will be a lot of extra traffic.
In fact, the impact of this kind of system on mail could be pretty bad if widely adopted: large amounts of mail may end up being held up in delivering servers, and "informative" messages sent by helpful mail systems (about "temporary failures") may end up creating more junk mail than they avoid.
Yes, I realize that for "serious" science still expect things to be published in peer reviewed journals, but in most cases I can't help but think that getting the article out there would be more useful. Sure, peer review is important, and somewhere to look for some kind of verification of the value of a paper is useful. But I much prefer the Research Index way, where I can get a good indication of the value of a paper by looking at how many people have cited a paper and WHO have cited a paper.
Anyway, pretending that putting up a document on a website is somehow less publishing a paper than having it printed in a journal, is just plain elitist. You should propably be a bit more critical to papers that are published that you don't know have been through a proper review, especially if you're not a domain expert yourself, but being aware of the source is something that you always need to be.
Prevent email address forgery. Publish SPF records for y
It seems one side effect of this approach is that it records the sender and recipient of every email sent through a particular mail server.
Sound familiar to anyone?
The comments in this paper about other systems ignore one of the oldest and largest SPAM filters: SpamAssassin.
SpamAssassin can also be used at the MTA-level, and while this tool might be an interesting test to integrate with SA, its claims that other systems cannot feed back to the sender that their mail has been blocked is flat-out wrong.
Most people do not do this because you are almost certainly getting this mail through a relay, and that relay is going to get the SMTP temporary error and try to send a warning to the user who sent it. Spammers regularly slam my home mail server by using my address as the "From" in an entire batch of spam. It's pretty seriously annoying to get that deluge of junk, and it's not really necessary. If your spam system just identifies spam and lets the user (or sysadmin) decide how to deal with it based on how "spamish" it is, you get a much more reasonable behavior.
I junk thousands of pieces of spam every week, and I *never* junk valid mail. Yes, I do have some spam in my inbox. Most of it is tagged as potential spam, and I delete that after cursory inspection of the from addresses. Some of it is missed, and the overhead that I suffer having to identify that myself is amazingly low compared to not being able to read my mail prior to SA.
Check out SA. The latest version is pretty impressive, and if this "new" technique (I don't think the idea of tracking connection quality is very new, it's certainly done in SA to some extent) turns out to be useful... well SA works on much the same principal as Perl: There's More Than One Way To Do It. Bayes, Blacklists, Whitelists, Obfuscation detection, Checksum trackers, you name it, SA uses it. None of these techniques gets to say "this is spam", they all just get to poke a message in the direction of being spam or non-spam. This leads to something far more reliable than any one techniqe.
The key is to make spammers not make money!
If people start adopting anti-spam technologies we would reduce the return spammers get from sending spam. Reduce this enough and the spamming business will no longer be profitable.
POPFile is great. I've also used SAProxy (http://saproxy.bloomba.com/) under windows and it works great too.
Again, the idea is not to eliminate all spam, but to reduce the return rate, and therefore the money made by spammers.
the sender level.
Like, say, putting a maximum limit on the number and size of e-mails that can be sent out a day.
Gather studies on how many people send 1 to n e-mails a day, and how many people send out e-mails of 1 byte to n bytes in size.
My guess is, it's a pretty distorted curve, with maybe a few thousand people -- of all those online -- sending out millions of e-mails a day. The maximum most "normal" people will send a day is probably 100 (and that's a large over-estimate).
social sciences can never use experience to verify their statemen