Hopefully this is an acceptable subjective question. We are interested in your specific and recent experiences.
For years, we used the “hidden field” trick to confuse spambots into not being able to deliver spam via an online form. In particular, this solution from Nfriendly worked perfectly.
Over time, though, spambots got smarter, and it no longer stopped much. We removed the previous solution during a site redesign because it didn’t work well with the new setup. Spam continued, albeit not at a noticeably higher rate.
We would like a new solution that blocks at least most spam without having to resort to a captcha that could discourage user interaction.
There are lots of good posts on StackOverflow about various methods to try and stop, or at least reduce, spam via an online form without using a captcha, but most of them are rather old and tend to be discussing techniques that probably also have been defeated by now like the hidden field solution.
In your recent experience, have basic math problems in lieu of a captcha been defeated already? Has it discouraged user interaction? How about this clever idea of displaying a photo of Mario on a video game site and asking the user to identify him? In your experience, are spambots smart enough to defeat that method?
It seems like the most recent ideas to avoid a captcha are trying to detect human-like activity, but these may add quite a bit of overhead.
Before attempting to implement one of the most recent ideas or try to roll our own, some community feedback would be helpful.
Based on your recent experience, what do you think is the current, best, lightweight solution for reducing spam submitted via an online form without using a captcha? Why? Thank you.