Protection against phishing, malware, and other threats targeting email and collaboration tools in Microsoft 365
Follow these steps to get protection working again and then contact support if needed.
- Restart the laptop
- Close all apps and restart Windows. This can fix temporary issues with the Defender service.
- Check that Microsoft Defender Antivirus service is running
- Select Start and type
services.msc, then press Enter. - In the Services window, find Windows Defender Antivirus Service.
- Make sure Startup type is set to Automatic.
- On the Action menu, select Start.
- If Start is greyed out, select Stop, wait for it to stop, then select Start again.
- Note any error messages that appear during this process.
- Remove third‑party antivirus that may be disabling Defender Some third‑party security products can turn off Microsoft Defender.
- Select Start, type
appwiz.cpl, and press Enter. - In Programs and Features, uninstall any non‑Microsoft antivirus or security suites.
- Restart the laptop.
- Caution: While third‑party security is removed and before Defender is working, the device may be unprotected.
- Run Microsoft malware tools once Defender is working If Defender starts successfully but still reports issues:
- Run a full scan with the built‑in Malicious Software Removal Tool:
- Press Windows logo key + R.
- Type
%windir%\system32\mrt.exeand select OK. - Approve the prompt and follow the wizard to perform a full scan and clean.
- After the scan, restart the laptop.
- Install the latest Windows and Defender updates from Settings → Windows Update.
- If Defender still will not start or errors continue
- Run Windows Update to ensure the latest Defender components are installed.
- If Defender continues to show errors during scans or startup, use the Feedback Hub (Windows logo key + F) to report the issue and then contact Microsoft Support.
- Contact a Microsoft support representative If the device still reports viruses and Defender remains disabled or cannot be started:
- Go to the Microsoft Support site and choose the Security or Windows Defender product family to reach support options.
- Alternatively, use the Get Help app in Windows:
- Open Start and search for Get Help.
- Describe the Defender/virus issue.
- Choose Contact support, then select chat or request a callback from a support agent.
If at any point malware prevents downloading tools like Microsoft Safety Scanner, a Microsoft Support agent may be able to download and run it remotely after you contact them.
Also be cautious of fake virus alerts or pop‑ups that tell you to call a phone number; real Microsoft warnings never include a phone number.
References:
- Troubleshoot Windows Defender or Endpoint Protection client
- Antivirus and antimalware software: FAQ
- Troubleshoot problems with detecting and removing malware
- Microsoft resources and guidance for removal of malware and viruses
- You cannot download the Microsoft Safety Scanner because of a malware infection
- Tech support scams
- Protect yourself from online scams and attacks
- Protect my PC from viruses