Krikor,

Not sure what you mean by "Since this view uses Joomla!'s core hooks you can try this extension as well." -- Enabling stopforumspam didn't help. I am still getting fake registrations. Here's the latest one:



What can I do next?

It means that the registration is a core Joomla! part. K2 simply extends it with a few fields, it does not replace it. You can try searching for security extensions in the JED.
extensions.joomla.org/category/access-a-security/site-security