March 8, 2007

...Learn TDD with Codemanship

Pet Pics Block SPAM-bots

I read on this morning about a new method of protecting web services like email and message boards from SPAM-bots.

The usual method for preventing this is to ask the user to read some text that's embedded in a "noisy" image which, it's hoped, a piece of software would find very difficult to read. It's a kind of Turing Test designed to distinguish between a human user and a software user.

The problem is that clever programmers have managed to get around this and create code that can read the text. In other words, they've figured out how to pass the test and fool our security system.

So some even cleverer folks have decided to make the test much, much harder. Using photos of homeless cats and dogs, users are asked to pick out the pictures of cats before they can submit the form. While any fool can distinguish between a cat and a dog, even from a vague silhouette, apparently computers simply can't do it.

A cat and a dog yesterday

That's because the difference in shape between a cat and a dog is very, very fuzzy indeed. (Ask yourself the question "I know it's a cat because...?") Our brains do well with complex and fuzzy problems like this, but computers really struggle.

I suspect this new test has cleverly exploited the real difference between humans and computers, which is that we are capable of solving non-computable problems.
Posted 14 years, 1 month ago on March 8, 2007