Error Code: 0x80070424 - Windows Defender doesn't update

Manually install the latest Microsoft Defender protection update first; if error 0x80070424 remains, check whether Defender or Windows Update services are unavailable before repairing the update engine.

1. Install the protection update manually

1. Open Microsoft’s latest security intelligence updates page: https://www.microsoft.com/wdsi/definitions/antimalware-definition-updates
2. Download the package matching your Windows architecture—usually 64-bit on current PCs.
3. Run the downloaded file as administrator.
4. Restart Windows.
5. Open Windows Security → Virus & threat protection → Protection updates → Check for updates.

Microsoft recommends manual installation when Defender repeatedly encounters update errors.^1^

2. Check Defender service health

Right-click Start, select Terminal (Admin) or Windows PowerShell (Admin), and run:

Get-Service WinDefend, WdBoot, WdFilter, WdNisSvc, WdNisDrv,
  SecurityHealthService, wscsvc, wuauserv |
  Format-Table -Auto DisplayName, Name, StartType, Status

Check these results:

• WinDefend should normally be Running when Microsoft Defender is the active antivirus.
• SecurityHealthService and wscsvc should be available.
• WdBoot being stopped after startup is normal.
• wuauserv is the Windows Update service.

Microsoft documents the expected Defender service states and recommends investigating stopped or unavailable components.^2^

If wuauserv exists but is stopped:

1. Press Windows+R, enter services.msc, and press Enter.
2. Open Windows Update.
3. Select Start.
4. Retry the Defender update.

If a service reports “Cannot find any service”, do not download registry files or service-repair scripts from third-party sites. That indicates a deeper Windows component or policy problem requiring the repair steps below.

3. Confirm Defender is the active antivirus

Open Windows Security → Settings → Manage providers → Antivirus.

If another antivirus is listed as active, Defender may be disabled and therefore unable to update. Uninstall the non-Microsoft antivirus through Settings → Apps → Installed apps, restart, and check the provider again. Some antivirus products require the vendor’s cleanup utility after normal removal.^2^

On a work-managed computer, do not remove corporate security software; contact the administrator instead.

4. Reset Defender’s definitions and update directly

If Defender is active and its services are running, open Command Prompt as administrator and run:

cd /d "%ProgramFiles%\Windows Defender"
MpCmdRun.exe -RemoveDefinitions -All
MpCmdRun.exe -SignatureUpdate -MMPC

Restart Windows and check for updates again. Microsoft documents removing the current definitions and requesting a fresh signature update as part of Defender recovery.^3^

5. Repair Windows components if services are missing or commands fail

Run these commands in Command Prompt as administrator, in this order:

DISM.exe /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Let each command finish completely, restart Windows, and retry the update. DISM repairs the Windows component store; SFC then checks and replaces damaged protected system files.^4^

If DISM fails because Windows Update itself is unavailable, or the required services remain missing afterward, use an in-place Windows repair installation or contact Microsoft Support. Avoid a clean installation until repair options and backups have been considered.

References

1. Troubleshoot problems with detecting and removing malware | Microsoft Support
2. Troubleshoot Microsoft Defender Antivirus service startup problems
3. Troubleshoot Microsoft Defender Antivirus Security intelligence not getting updated
4. Use the System File Checker tool to repair missing or corrupted system files | Microsoft Support