iPhone hacked message, real or spam?

My iphone 6S Plus screen indicated my phone had been hacked when I opened DuckDuckGo’s web search page. How do I know if it was valid or spam? I just closed the app after taking a screenshot that is attached. It tried to make me choose either “OK” or “Check Source” or something similar to that. Instead, I closed the DuckDuckGo app.

Can your iPhone actually be hacked and how can I protect my phone and files?