Captchas were (and probably still are for the moment) a good way to defeat automated spammers.
They are those deformed letters and numbers that you, as a human, can still recognise and type in, but which a computer program cannot because they do not correspond to the letters they know and the slanting changes randomly. They are used on websites for everything for posting comments to blog to signing up for new accounts.
But now hackers, ever inventive, have found a way around this. In this bbc news article is told that hackers are using human (ahum ‘male’) fascination for nakkid women to a new level. For every layer of clothing that gets removed you need to respond to a captcha. And the thing is, these captchas are dynamically retrieved from other websites, where the response to these captchas is used to post spam comment or using a program to auto-signup for a new account !
Very clever ! We’ll have to find a new way or a new variation on captchas.