This page describes the process of turning on Windows Defender (Anti-Virus) on a PC computer. Windows Defender can help protect your computer from viruses and other unwanted malware or ransomware that can try to steal your computer data, personal identifiable information and/or monitor computer activity.

If you believe your computer may have been infected by a computer virus, malware or ransomware, please contact the IT Helpdesk by email at, by phone at 562.903.4740 or by coming to the Helpdesk in Tech Commons on middle-level of the Library.

How to Turn On Windows Defender on a PC

StepWhat to doHow to do it

Click on the Windows key.

2Search for and selectWindows Securityfrom the search results.

3Ensure the Virus & threat protection section has a green check mark and says, "No action needed."


If the Virus & threat protection option has a red circle with an x and says, "Turn on" your antivirus is disabled will need to turned on.

Note: If you need to turn on Windows Defender, it, it may be wise to run a Quick scan from the Virus & threat protection page to ensure your computer is clean.

How to Turn On Windows Defender:

  1. From the Windows Security page, select Virus & threat protection.
  2. Click Manage settings.
  3. Ensure the following options are turned on:
    • Real-time protection
    • Cloud-delivered protection
    • Automatic sample submission
    • Tamper protection

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