I took some time out this weekend to upgrade Movable Type to the newly released 3.2 version. Despite appearing to be a small number increase in versions, it actually contains a huge amount of enhancements and new functionality, much of it focusing on combating spam.
Not so long ago, I took some measures to deal with comment spam, but trackback spam almost immediately picked up and the options for dealing with trackback spam were, at the time, very limited. For those unaware of the concept, the trackback system is a way for a website (it was designed for blogs, but could be applied to any website) to list out other websites that link to the first website. This is accomplished by allowing people to "ping" an entry, thereby alerting that blog that someone has linked to that entry. The site receiving the ping typically displays the trackback information (typically including a title, a link, and a short excerpt) below the entry. It's an open system, meaning that anyone can ping any site they want, even if they haven't linked to that site. And that's why the spammers love it.
After getting hit by a few hundred spam trackbacks one week, I decided to completely disable trackbacks on my blog, but I found that my options were limited. There was no easy way to do so, though I did eventually find a way that was easier than going back to every entry and disabling it manually. Then Six Apart announced that they were working on the 3.2 release and that it would include all sorts of ways to deal with trackback spam. For one, they've included a quick and easy way to disable all trackbacks (without having to resort to fiddling with the database directly), but they've also included some interesting spam filters which appear to be working well.
It seems to be working well so far, but I'm still considering whether or not to keep trackbacks. Aside from the spam, there are a lot of other issues with it. It's not like everyone uses it. In the past few years, I've been linked by other blogs many times, but I've only gotten something like 5-10 trackbacks (and I lost several when I upgraded my database). But the whole experience has got me thinking about open systems and the potential for abuse. On the internet, it seems like such systems are almost always ruined by spam. It would be a shame if a service like del.icio.us were ruined by spam, but at least it isn't quite as open to blatant abuse as trackbacks were, so perhaps there's a chance.