writes to tell us about a twist he has developed on the common Captcha
technique to discourage spam bots:
HECs encode the Captcha image into HTML
, thus presenting an unsolved challenge to the bots' programmers. From the writeup: "The Captcha is no longer an image and therefore not a resource they can download and process. The owner of the site can change the properties of the Captcha's HTML, making it unique,... add[ing] another layer of complication for the bot to crack."
HECs are not exactly lightweight — the one on the linked page weighs in at 218K — but this GPL'd project seems like a nice advance on the state of the art.