Plan for Spam, Version 2

bugbear writes "I just posted a new version of the Plan for Spam Bayesian filtering algorithm. The big change is to mark tokens by context. The new version decreases spams missed by 50%, to 2.5 per 1000, even though spam has gotten harder to filter since the summer. I also talk about how spam will evolve, and what to do about it."

Comments

Spamassassin and ENDING spam....

[ajs]

The latest development Spamassassin has an interesting application of Bayesian filtering. Basically, it takes all of SA's existing heuristics, uses that to develop a sense of what is and is not spam, and then pumps the results through a Bayesian filter that learns from these messages.

As with any other SA test, no single element of the chain is trusted enough to definitively call something spam, but if a message would have squeeked through before, this new filter can put the final nail in its coffin through word analysis against previous spam.

So, why did I use a subject about "ENDING spam"? Because one of the tools that spammers have is SA itself. They can use it to score their messages and determine how "spamish" it is. The problem now is that each SA installation will have subtly different scoring, and the message may be "ok" according to the spammer's version, but my version has a better sense of the mail that *I* get.

SpamAssassin is definitely a tool worth checking out if you have not already. Install it in daemon mode (spamd) and then use "spamc -f" in your procmailrc or the equiv for your MTA.

Very nice tool, and a real time-saver for me.

Obligatory plug for TMDA

[Silas]

I'm really excited about all of the neat stuff happening with Bayesian filtering and related technologies, but I just wanted to put in a plug for TMDA, Tagged Message Delivery Agent, which uses a whitelist-centric strategy. Since I began using it, the amount of spam I have to look at is virtually at zero. If you haven't read about it yet, check it out.

Spam Archive

[Doctor Beavis]

The article mentions compiling a vast collection of spam. Such a project is already underway at SpamArchive.

Re:base64 encoded emails....or images

[GGardner]

A common thing that spammers to do try and trick filters is use

Content-Type: text/html (or text/plain)
Content-Transfer-Encoding: base64

Because a lot of filters don't know how to decipher this. For me, this makes it a lot easier to filter, though. I get no legitimate e-mail encoded this way, so I just have procmail dump any e-mail encoded this way. Problem solved, and without the CPU burden of decoding or running expensive spam filters.

popfile URL

[roalt]

Popfile can be installed as an intermediate between your mail-server and your program, and you can add tags to your mail to decide in which 'bucket' your mail belongs to.

The url for the project is popfile.sourceforge.net

I didn't try it yet, but it I will try it really soon now!

Re:Spam needs a global solution (Global Solution)

[minas-beede]

OK, signal and noise. What if the signal was all in one frequency band and the noise all in another. Problem separating them? No.

What if, in effect, a similar distinction held for spam in the transmission channel - that spam by itself selected a pathway to the recipient that was never used by the signal? Block that pathway and the spam never gets through.

Spam doesn't select a pathway but spammers do. If you could block relay spam at the open relays it would be dead. You can't, of course - the open relays are controlled by people who don't know the need to block spam. You know that, I know that. If you can't change the people then change the open relays (from the spammers' points of view.) Set up a system that looks like an open relay and stop the spam. An open relay honeypot.

I asked an operator of such a honeypot how he did last year:

> How did 2002 end?

From March 7 to December 26 2002, the total was:

235,624,232

Using one Pentium 90 he stopped spam to 235 million recipients. Think about that number when you see filter people reporting what they stop just for their own domains. This was spam to recipients all over, not simply to the honeypot operators domain: he operates at the relay level. He stopped 100% of the spam, no deception deceived him, no tuning was needed, no valid email was caught - it is perfect filtering. Perfect filtering - who else has that?

And you can do it at home on your DSL or cable connection (the guy above uses sendmail -bd, but Windows users have a program they can use):

http://jackpot.uk.net/

Yeah, I know, spammers are switching to open proxies. So, write an open proxy honeypot. That, too, will be 100% efficient. In addition you now are giving spammers reason to fear every open relay and every open proxy they detect. FEAR. The SPAMMERS have to scramble. They have to scramble and they have to show everything they do to overcome the technique - there is no stealth way to look for open relays and open proxies.

The problem is solved, it is a matter of implementation and of getting active systems everywhere in the net space (so there's no safe IP space for the spammers anywhere.)

Remember: A single Pentium 90, 235 million spam messages stopped in 10 months.

Re:Why can't we have legal restrictions on spam?

[babbage]

Please take a look at my notes on last week's spam conference, and in particular the Jon Praed notes (near the end; two speakers came after him).

Praed argued, very eloquoently & persuasively (hey, he's a lawyer :) that there are laws on the books banning spam in nearly every state. All you have to do is find a way to bring those laws to your assistance. In particular, note that:

• Ever have a hard time tracking down a spammer? Ever have one that spoofed message headers? Gee, that sounds like fraud, doesn't it? Indeed it does -- much or even all spam can be considered as fraud, and as such you can attack it from that angle anywhere in the country.
• Laws are pending in various jurisdictions to outlaw spammers' bulk mail software. The catch here is that there is a lot of legitimate bulk mail software that can be abused -- think majordomo, MailMan, etc -- so any laws crafted will have to include clauses that protect legitimate use of such software while banning UCE somehow. Watch for this to develop over time.
• Suggestion: if you get spam that mentions a trademarked product (Viagra, pirated copies of well known software, etc), forward the message to the holder of that trademark. They will almost always be keenly interested in this abuse of their trade name, and will take it upon themselves to go after the spammer.
• If you are in the habit of reporting spam to an organization like SpamCop, do so as quickly as possible: spammers are getting in the habit of leaving their ads up long enough for recipients to respond to, but pulling them down before investigators get a chance to scrutinize anything. The faster these groups can analyze the sources of spam, the better the chances of getting all the way back to the source.
• Final and most important point: the precedent set by the Verizon vs. Ralsky case was very valuable to anti-spam efforts. First, that spam prosecution can be carried out in the jurisdiction that the harm occurred, not where the person doing harm was when causing it. So if California has anti-spam laws, they can potentially be used no matter where the spammer lives. Praed practices law in Virginia, so I'm assuming that their laws are amenable to this kind of application. Second point: ignorance about an ISPs acceptable use policies (AUP) are no defence in court -- certain etiquette standards have emerged over time, and it is assumed that the sender of UCE has to be aware of these standards. As a result, if your ISP has an AUP that forbids UCE, this can be a tangible protection for you in court. This is very good news!

As a lawyer that has successfully prosecuted a number of spammers, Praed was able to talk about all of this with some authority. He cautioned everyone though that laws will never eradicate spam -- as he put it, "people still rob banks since that's where the money is". But legislation & prosecution can still be a very valuable tool in fighting spam, and an important supplement to things like better mail filters. This is a big problem, and is going to need a variety of tiered solutions to control it.