Possible fake virus (malware?) when trying to log onto YouTube

I am receiving a claim that my ip address was stolen to install a virus-- and I have a "lock" on my MacBook. This happened when I tried to log onto YouTube. They tell you not to shut it down and I shut it down anyway, and now I find I can use my MacBook normally in every way, but I can't log onto YouTube from doing a Google search. I can bypass it by using a YouTube link to a certain song or video. But each time I try to go straight to YouTube, my computer locks again and I have to start over. Is there a way to remove this malware (or whatever it is) without going to Apple Store? If it's a simple solution, I would appreciate any help. They tell you to call 88*** and identify themselves as Apple. But of course they aren't Apple and I'm not going to call them. Thank you.

[Edited by Moderator]