abusive registrations

Hi there!
I notice that I have a lot - unfortunately almost exclusively - registrations from people with weird names and countries who are not even supposed to speak the language and never post any questions. Its mostly from Poland and Rumania and so on. Some time ago, when I was running easyblog on the old version of this website, I noticed that some people abused the blog to communicate with each other. Do you have security issues? What is this about those unrelated registrations?
To the best of my knowledge, my systems are up to date. I've also attached a screenshot.

Thanks for your advice,
Chantal