Strange virus-like message on my iPhone!

Several times since I bought this iPhone a full-screen message popped on it's screen. The message's text is Gibberish, and it's a different text every time, as you can see in the pictures, with a "dismiss" button on the bottom. I am afraid the dismiss button will do something bad to my iPhone, which is why I never pressed it. While the message is on-screen, I can lock my iPhone, but when I try to open it I see this message again instead of the lockscreen. The home button doesn't do anything, either, and the only way I found to get my iPhone working again is shutting it down. It's quite annoying, and I'm afraid it is a virus.

Anyone knows what is it? What does it mean? How can I get rid of these messages?

Thank you very much in advance!