Windows 10: Whilst browsing a what looked like a bona fida Windows Defender warning appeared on full screen

Whilst browsing a what looked like a bona fida Windows Defender warning appeared on full screen, stating I needed to do an immediate scan with link provided, as there were three serious infections on my computer.

I immediately closed all open apps, did scans with Defender and Mbam, both stating clean....did think about doing a print screen prior to closing down, but decided not to take a risk.

I cannot over emphasise how authentic this warning appeared including M$ logo.

:)

 

warning message when startup

Hi,

Thank you for posting in Microsoft Community and being a part of Windows 10.

I understand your concern about accessing the operating system with the warning message and slow performance. We will help you with this issue.

Do let us know the following to assist you better with this issue:

• What is the complete error message/ error code of this issue?
• Have you made any changes to the operating system prior to this issue?

Try few of the below troubleshooting steps and check if it helps.

Method 1: I suggest you to Run System Maintenance Troubleshooter.

It finds and clean up unused files and shortcuts and performs maintenance tasks.

Follow:

• 
  Type Troubleshooting in the Search box from the desktop.
  
• 
  Select the Troubleshooting option.
  
• 
  Select View All option and select the
  System Maintenance.
  
• 
  Click on Next to perform the System Maintenance troubleshooter and follow the steps.
  

Method 2: I suggest you to boot the computer in Safe mode with Networking and check if this issue persist.

Refer: Start your PC in safe mode in Windows 10


Follow the below steps to place the computer in normal mode.

• Press Windows + R keys to open Run
  command.
• Type msconfig and press Enter.
• In the System Configuration window, click on
  General tab.
• Select Start-up selection as Normal startup, click on
  Apply and Ok.
• Follow onscreen instructions.

Method 3: I suggest you to install he pending updates on your device.

Steps:

• Connect to the internet.
• Press Windows key and type
  updates.
• Click on Check for updates.
• Under Windows Updates, click on
  Check for updates.
• Try to install the updates being shown.

Hope it helps. Try the above and get back to us with an updated status of this issue for further assistance.