I wonder why they have the silly 2 + 3 = ? thing in their form at the bottom of the homepage. It's text/html, so it can't be anti-bot and seems like pointless for a human... Does anyone else know the logic behind that?
I don't see the field you're referring to, but I'll try to answer with a best guess anyway. Most web spam bots fall into two categories: 1. They target a certain web software package (such as WordPress), for which they know the HTML layout and the range of possible CAPTCHA challenges. 2. They try to fill out every HTML form they find blindly, using heuristics based on the names of form input elements. To defeat both,…
PS: it's a the bottom of the landing page (not signup)