Defensio has announced the public-beta launch of its new spam filtering service for blogs and other social web applications. The new service is free for individual users. It currently only supports WordPress-based applications, but a public API for interested developers is freely available, and support for other web services is on the way.Defensio in its current form is a replacement plug-in for the Akismet anti-spam module on WordPress. It aims to put an end to inconvenient "Reverse Turing" authentication tests (where the user has to prove that they are human by entering image-based letters, or solving a simple math problem) by analyzing with the central Defensio system. A "spamminess" score is assigned to each comment, and if the score is high enough, the comment will be queued for moderation. The filter learns over time what is spam and what is not, and Defensio claims it is currently up to 99.4 percent accurate with regard to filtering the wheat from the chaff. (For those concerned, that is better than most employment drug tests.) The "spamminess score" thing is a pretty good idea - when it comes time to moderating suspect comments, the material with the lowest scores rise to the top of the queue, while the obvious spam sinks to the bottom. Making "false positives" (we know where your mind went just then!) easier to locate improves the system as a whole, so you get a better filter as time goes on. Defensio also compiles a digest of your recent comments and sends them to you via RSS feed, and provides a periodic detailed report on what it's been up to. The system is free for individual users, and installation appears to be a very straightforward affair. Medium-size commercial users can avail of the service for between US$ 5 and US$ 15 per month, while large web presences attracting over 300k comments a month, or representing a company turning over US$ 10 per year, can have their comments Defensio-d for $50 per month for the first license, and US$ 30 per license thereafter. The war against comment spammers is has been waging since, well, since as long as there have been comments boards to spam. One method employed by Google and Wikipedia, amongst others, is to insert a “rel=nofollow” attribute as standard to all external links contained in Comments, which stops a search engine from crawling the link, and makes the act of vandalizing your blog a lot less worthwhile. If you're interested in Defensio's intelligent comment filtering process, however, check out the Defensio website for yourself.