Spam: I’m quoted in
New Scientist! w00t!
This is interesting and promising technology. But like all antispam techniques, spammers will find a way around it. Once spammers get a copy of the software, they can create and test countermeasures in the comfort of their own sleazy lairs.
It’s worth talking about this. Newsflash: spammers have no difficulty testing their spam against closed-source spam filters, even when they can’t ‘get a copy’ and test them in ‘their sleazy lairs’.
How do they do it? Easy — just set up an account at a site that uses that filter (AOL, Yahoo!, Hotmail, and GMail, it’s pretty obvious how to do that; for other closed-source filters, find an ISP that uses it). Then send ‘test mails’ repeatedly to that account, and apply trial and error to see what gets past the filter and what doesn’t. Eventually, they figure out what works for that filter, and what doesn’t.
How did I figure this out? Well, I came across the manual for the Send-Safe ratware on-line. It noted that the ‘hashbuster’ randomisation technique, which we in the SpamAssassin team had long assumed was intended to block hash matches by DCC, Pyzor and Razor, was in fact intended to block AOL’s implementation of that system. The open source ones weren’t even mentioned.
Update: found it — from their FAQ:
Mime Encoded content
If you want to get into AOL… use it.
MIME encoders allow you to send documents written within a specific application through email without causing readability or formatting problems. For example, you can send a letter created in MSWord with and be certain that it arrives at its destination in the same format by encoding it with MIME first. The recipient then decodes it back into the original MSWord format.
That isn’t why we use it though.
We use it to cause ‘uniqueness’.
When you put a rotate tag at the beginning of a MIME encoded email, it causes everything after that point (including checksums) to be ‘different’ in every message.
Why is that that important?
Because it throws off filters that look for many copies of the same message to nuke.