Visitors to our web-site, and indeed to other web sites, may have noticed this ReCaptcha logo on its pages.

Like just about every web site on the planet, we have at times been inundated by spam where automated computer scripts known as bots try to automatically fill in forms to send marketing messages to web site owners, for whatever nefarious purpose they think it might achieve.

For some time, web site operators have used various methods to try to filter out the bots and ensure that only humans fill in the forms. Some of these methods include distorted letters, questions easily answered by humans but less so by computers (e.g. “what is the third word in this list?”), or my favourite: “tick this box if you are not a robot.”

The latest version is v. 3 which requires no human interaction at all. It sits in the background analysing the page clicks and interactions with the page to try to work out whether the user is likely to be a person. Bots are rejected and people are allowed through. If there is a grey area, a challenge screen is opened to try to confirm the identity of the user.

No doubt, a v. 4 will be needed soon as the arms race between web sites and invasive bots continues.