Windows Malware attacked my Mac

[kimichan]

I purchased and installed Malwarebytes for my MacBook PRO.  It seems to have worked very well until last week.  What should have been a perfectly safe link to click on  (from the main Yahoo! News Page), I was suddenly trapped in one of those scams saying that my Windows OS (!!!!!) had a bug and if I didn’t call the displayed number w/in 3 mins they would permanently disable my system  Ditto if I tried to shut down. I ran Malwarebytes and it found NOTHING.  I couldn’t close Safari or shut down my system - not normally, or using the shift-control-option + power button.  I just closed the laptop and gave it some time figuring that eventually the idiot code would try to do something window-ly that wouldn’t work and would give up.  When I re-opened the laptop about 10 minutes later, everything was back to normal.  I ran Malwarebytes again and it found nothing but how can I trust this?  Some advice please....  kimichan

[alvarnell]

This is almost certainly not being caused by anything on your MBP. Such popups are commonly caused by a javascript embedded in an advertisement on the site you went to, so called "malvertising". Such sites subscribe to an advertising service that occasionally has one of it's rotating advertisements infected which causes that popup. They are perfectly harmless as long as you don't take any action on what it is telling you. Eventually the ad goes away along with the persistent script. Sounds like everything is back to normal.

Command-option-escape should give you a Force Quit Applications window that you can use to force quite Safari. Or you can hold the option key down while clicking on the Safari icon in the Dock and selecting "Force Quit" from the resulting menu. Then hold the shift key down when re-launching Safari to prevent it from re-opening windows and tabs.

Shift-Control-Option-Power key is used to reset SMC after a reboot, so not surprising that this didn't result in a shut down.

• Command-Control-Power key will force a reboot. 
• Command-Control-Media Eject button will quit all apps and restart. 
• Command-Option-Control-Power Button will force a quick shutdown or you can hold down the option key and select "Shutdown" from the Apple menu.

[treed]

Al is correct. This is not malware. It's a website trying to trick you into believing that you're infected with malware, so that you will do whatever it says to do (generally, either calling a phone number that will connect you with a scammer, or downloading and installing scam software).

Al's advice for force quitting Safari, then re-opening Safari while holding down the shift key, should work. There is never any reason to force your Mac to reboot over something like this. In fact, forced reboots should be avoided whenever possible.