For the longest time we’ve been using a fairly basic captcha software to prevent robots from signing up for accounts on the Battlestar Wiki. This has changed.
We now use a captcha service provided by “reCaptcha“, which can be integrated into any MediaWiki painlessly. Essentially, the captcha is graphical (or by sound for the visually impaired).
If you wish to set this up on your own MediaWiki-run wiki/site, the instructions are here.
The service is active across all wikis. Any problems should be reported to me.