After migrating a Magento webshop to a new host, there suddenly these 2 last days appears hundreds of fake user registration users. They have name like nzyaffmrtk , lrdrbzcuca and weird emails.. Does anyone know why? What can I do to stop this? With out adding an extension that will rewrite the core files.
You could possibly add what one would call a 'bot trap' into your registration page. You see, bots don't have eyes. And without eyes the only way to fill out a form is via field automation. Therefore, they must 'feel' for the fields within a form. So, how do you trick a blind robot? You create an invisible field called something official sounding like 'nickname' and then filter your applications thusly.
How does this play out in the real world? A person, being non-mechanical and (hopefully) having at least one optical field searching mechanism will never find (nor click, nor type into) this invisible field. However, robots, being very much the opposite will happily fill out every single field on the page.
In the backend just reject all applications with this field filled in.