scan alert

Two possible suggestions come to mind.

• Phony "tech support" / "ransomware" popups and web pages - Apple Community describes scam web pages and how to get rid of them, and
• Stop unwanted Notifications - Apple Community describes bogus Safari Notifications and how to stop them from appearing.

If neither one describes what you are encountering, please provide some more details. A screenshot or photo will help (use the "Image insertion" icon pictured below).

You didn't provide many details on this, but odds are it's a bogus notification. You'll want to turn off website notifications as per this: Turn off notifications for an app or website on Mac - Apple Support

Hope this helps.

Sam7713 Said:

"scan alert: I received an alert that there has been a security block put on my computer. How do I remove this and have access to my Mac again?"

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Getting Around Ransomware:

Mirror the Screen to this External Display:

Seems you have ransomware on your Mac. So, mirror the display to get out of this. Performing the following will mirror the Home Screen, and allow you to use it as if it were you laptop's screen.

• Without Touchbar: Hold Down [command + F1]
• With Touchbar: Hold Down: [command + dull screen]