I find it repeatedly shocking how stupid programmers are who work in supposedly security systems. Something like this is an absolute beginner's mistake! And such software is supposed to protect users from attacks from the Internet...
At heise online news there's the original article.
Ouch. Big hole in Moveable Type: the email addresses entered for sending entry notifications are not validated. This gives attackers the opportunity to abuse it - for example, according to this post, spammers have used the hole to send spam. A patch is also provided there that you can use to add validation, so that spammers can no longer easily abuse MT.
So, people, patch your Moveable Type! Or better yet: get rid of the script!
Not exactly new anymore, but perhaps worth considering for some of the current weblog spam fighters. I agree with Mark on many points: simple filter lists are the dumbest idea you can have when fighting spam, regardless of the medium. The fact that these filter lists are being positioned as a great new idea in the weblog space again is truly amusing.
It seems we humans are programmed not to believe that even the hundredth reinvention of the triangular wheel is still a stupid idea...