The use of CAPTCHA to combat spam bots is also blocking people with disabilities and the feature should be removed from websites, argues a group of disability organisations.

The completely automated public Turing test to tell computers and humans apart, abbreviated as CAPTCHA, is a popular measure deployed by webmasters around the world to prevent spammers from automatically sending unsolicited commercial messages to sites and users. It requires people to interpret characters and numbers that are difficult for machines to parse, and enter these as part of logging in to a site, for instance.

However, the dark side of CAPTCHA is that it hinders people with vision impairments to the point that they cannot use sites. Screen readers and other accessibility tools used by blind people often fail on distorted and illegible CAPTCHA text.

Now, disability groups such as Blind Citizens Australia, Able Australia, Media Access Australia and the Australian Deaf-Blind Council are calling on organisations to stop using CAPTCHA, setting up a petition with the Australian Communications Consumer Action Network — via redwolf.newsvine.com

The biggest issue with audio CAPTCHA is actually the same as with the visual version: just as it’s often hard to see which individual letters are being used, it’s hard to distinguish individual sounds. One of the problems with audio CAPTCHA that I’ve found is similar to the visual CAPTCHA: there’s so much noise behind the words that are being spoken you can’t identify what they are, Hawkins said.

That noise is added to block automated recognition systems, but in this case the cure seems worse than the problem. I pride myself on being a pretty good listener, Hawkins said. Because I’m blind I need to use my hearing in different ways and I find even with that very acute hearing that these audio CAPTCHAs are really difficult to understand.

A secondary problem is that audio CAPTCHAs often use numbers, but doesn’t distinguish them, so it’s impossible to know if you have to type 1 or one or won.

The solution, as we said yesterday, is to ditch CAPTCHA altogether. Sending a verification email is one solution, though that adds an extra step. Another good alternative is asking site users to solve a simple maths problem — an option that works well with screen readers, Hawkins said — via Lifehacker Australia