Windows Defender充当抵御可能影响您的计算机的任何恶意软件、间谍软件感染的第一道防线。Microsoft向使用^(Microsoft)Windows 10/8/7/Vista的客户提供此免费反恶意软件程序。它允许最终用户安排扫描或手动运行快速、完整或自定义扫描。

但是，有时，用户可能会遇到在Windows中^(Windows)启用 Windows Defender应用程序的问题。他可能会发现他的Windows Defender已关闭或无法正常工作。此外，如果您的Windows Defender自动禁用自身 – 每次启动Windows计算机时，或在您使用 PC 时随机出现，您可能需要调查以下几件事。

本文向您介绍了解决相同问题的故障排除过程。

Windows Defender已关闭或无法正常工作

您可能会收到一条消息：Windows Defender 已关闭，它没有监控您的计算机。^{(Windows Defender has been turned off, and it isn’t monitoring your computer.)}

如果您安装了其他防病毒软件，它将关闭Windows Defender。但是，如果您还没有这样做，那么您可能需要执行以下故障排除步骤：

1. 安装最新的 Windows 更新
2. 重新安装您可能已安装的任何第三方防病毒软件
3. 运行离线恶意软件扫描
4. 通过操作中心^{(Action Center)}启用Windows Defender
5. 检查 Defender 服务状态
6. 重新注册这些 DLL 文件
7. 检查注册表设置
8. ^(Perform)对WMI存储库^(WMI)执行一致性检查。

1]安装最新的Windows更新

检查您是否安装了所有最新的Windows 更新^{(Windows Updates)}，包括安装了最新版本的Windows Defender及其定义。

2]重新安装^(Reinstall)您可能已安装的任何第三方防病毒软件

您^(Did)最近是否卸载了任何安全软件——尤其是Norton或McAfee？如果是这样，它的部分卸载可能会导致问题。使用McAfee Consumer Products Removal Tool或某些防病毒删除工具^{(antivirus removal tool)}来确保您甚至删除了其残留物。

3]运行离线恶意软件扫描

您是否检查过您的计算机是否存在恶意软件？还是您刚刚从恶意软件攻击中恢复？我建议您下载并运行一个独立的便携式防病毒扫描程序，然后从您的^{(stand-alone portable antivirus scanner)}USB运行离线扫描- 或者使用在线防病毒扫描程序^{(online antivirus scanner)}服务来扫描您的 PC。

4]通过操作中心^{(Action Center)}启用Windows Defender

打开操作中心^{(Action Center)}，看看是否可以启用Windows Defender。

5]检查后卫服务状态

运行services.msc以打开Services Manager。确保Windows Defender 服务^{(Windows Defender service)}已启动并设置为自动。

6]重新注册这些DLL文件

如果 Windows Defender 的 Windows Defender 服务^{(Windows Defender Service)}( WinDefend ) 或Windows Defender^{(Windows Defender)}网络检查服务^{(Windows Defender Network Inspection Service)}( WdNisSvc )一直停止、关闭或无法启动，

重新注册以下dll文件，看看是否对您有帮助。在提升的命令提示符下依次运行每个命令，然后按 Enter：

regsvr32 wuaueng.dll

regsvr32 wucltui.dll

regsvr32 softpub.dll

regsvr32 wintrust.dll

regsvr32 initpki.dll

regsvr32 wups.dll

regsvr32 wuweb.dll

regsvr32 atl.dll

regsvr32 mssip32.dll

您可以使用我们的免费软件FixWin将^(FixWin)Windows Defender重置为默认设置。

7]检查注册表设置

运行regedit并导航到以下键：

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender

这里确保这些DWORDS的值为1：DisableAntiSpyware和DisableAntiVirus。

如果为 0，那么您将必须使用我们的免费软件 RegOwnit来获取这些注册表^(Registry)项的所有权，然后将其值从 0 更改为 1。RegOwnit 允许您使用^{(Windows Registry)}Administrator、Home Users或当前登录的^(Logged)用户^(User)帐户。

8]对WMI存储库执行^(Perform)一致性检查

Windows 安全中心^{(Windows Security Center)}也可能会提示您“检查设置”^{( “Check Settings” )}以进行恶意软件保护^{(Malware Protection)}，并且当您单击“立即打开^{(Turn on now)}”按钮时，它可能会显示错误消息“没有可供下载的新定义视窗卫士^{(There are no new definitions available to download for Windows Defender)}”。

问题可能是由不一致的WMI 存储库^{(WMI repository)}引起的。因此，重新启动WMI存储库应该有助于解决问题。

以管理员身份打开命令提示符^{(Open Command Prompt as an Administrator)}。键入以下命令并按Enter：

winmgmt /verifyrepository

如果您收到消息“ WMI 存储库不一致^{(WMI repository is not consistent)}”，请运行以下命令：

winmgmt /salvagerepository

这将对WMI存储库执行一致性检查并解决问题。重新启动您的机器。

立即尝试启用 Windows Defender。

如果您收到以下消息，则winmgmt /salvagerepository is failed, 请忽略此消息，并再次运行“ winmgmt /salvagerepository ”。这一次，它应该有所帮助。

这篇标题为无法打开 Windows Defender^{(Unable to turn on Windows Defender)}的帖子 提供了一些额外的故障排除建议，您可能也会感兴趣。您可能还想检查您收到的Windows Defender错误代码，并查看Microsoft是否有任何解决方案。

如果您的防病毒保护已过期，请阅读这篇文章。

您可能还想查看这些有助于解决 Windows Defender 问题的帖子：^{(You may also want to check out these posts which help troubleshoot Windows Defender problems:)}

• 错误 0x800106a，Windows Defender 无法打开
• 该程序的服务已停止 – 错误代码 0x800106ba
• Windows Defender 错误代码 0x800106ba：应用程序无法初始化^{(Windows Defender Error Code 0x800106ba: Application failed to initialize)}
• Windows Defender 错误：MSASCui.exe – 无法找到组件
• 错误 0x80070422 无法在 Windows Defender 中启动服务^{(Error 0x80070422 The Service Couldn’t Be Started in Windows Defender)}
• Windows 的错误 0x80508020、0x800705b4。
• Windows Defender 错误代码 0x800106ba 应用程序无法初始化^{(Windows Defender Error Code 0x800106ba Application failed to initialize)}
• 即使安装了第 3 方防病毒软件，Windows Defender 也不会关闭^{(Windows Defender will not turn off even when 3rd party AntiVirus is installed)}
• 无法打开 Windows Defender^{(Unable to turn on Windows Defender)}
• Windows Defender 不会更新定义
• Windows 无法安装以下更新，错误为 0x80070643
• Windows Defender PC 状态 – 可能未受保护
• 错误 0x80080015，激活需要在 CLSID 键下显示显示名称。

Windows Defender is turned off or not working

Windows Defender acts as the first line of defense against any malware, spyware infections that might have affected your computer. Microsoft provides this free anti-malware program to customers using Windows 10/8/7/Vista. It allows end-users to schedule a scan or manually run a quick, full, or custom scan.

However, sometimes, a user may experience issues enabling Windows Defender application in Windows. He may find that his Windows Defender is turned off or not working. Also, if your Windows Defender disables itself automatically – every time you start your Windows computer, or at any time randomly when you are working on your PC, here are a few things you may want to investigate.

This article explains you the troubleshooting procedure to resolve the same.

Windows Defender is turned off or not working

You may receive a message: Windows Defender has been turned off, and it isn’t monitoring your computer.

If you have another antivirus software installed, it will turn off Windows Defender. But if you do not and yet, then you might want to carry out the following troubleshooting steps:

1. Install the latest Windows Updates
2. Reinstall any third-party antivirus you may have installed
3. Run an offline malware scan
4. Enable Windows Defender via Action Center
5. Check Defender Service status
6. Re-register these DLL files
7. Check Registry setting
8. Perform consistency check on WMI repository.

1] Install the latest Windows Updates

Check if you have all the latest Windows Updates installed, including having the latest version of Windows Defender and its definitions.

2] Reinstall any third-party antivirus you may have installed

Did you uninstall any security software recently – especially Norton or McAfee? If so maybe its partial uninstallation is causing issues. Use McAfee Consumer Products Removal Tool or some antivirus removal tool to ensure that you have even removed its remnants.

3] Run an offline malware scan

Have you checked your computer for malware? Or did you just recover from a malware attack? I suggest you download and run a stand-alone portable antivirus scanner and run an offline scan from your USB – or else use an online antivirus scanner service to scan your PC.

4] Enable Windows Defender via Action Center

Open Action Center and see if you can enable Windows Defender.

5] Check Defender Service status

Run services.msc to open Services Manager. Ensure that the Windows Defender service is started and set to Automatic.

6] Re-register these DLL files

If Windows Defender Service (WinDefend) or Windows Defender Network Inspection Service (WdNisSvc)  of Windows Defender keeps stopping, turning off or could not start,

Re-register the following dll files and see if it helps you. Run each command in an elevated command prompt one after the other and hit Enter:

regsvr32 wuaueng.dll

regsvr32 wucltui.dll

regsvr32 softpub.dll

regsvr32 wintrust.dll

regsvr32 initpki.dll

regsvr32 wups.dll

regsvr32 wuweb.dll

regsvr32 atl.dll

regsvr32 mssip32.dll

You can use our freeware FixWin to reset Windows Defender to default settings.

7] Check Registry setting

Run regedit and navigate to the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender

Here ensure that the value of these DWORDS is 1: DisableAntiSpyware and DisableAntiVirus.

If it is 0, then you will have to use our freeware RegOwnit to take ownership of these Registry keys and then change its value from 0 to 1. RegOwnit allows you to take ownership of a Windows Registry key using Administrator, Home Users, or the current Logged On User account.

8] Perform consistency check on WMI repository

It may also happen that Windows Security Center may prompt you to “Check Settings” for the Malware Protection, and when you click the “Turn on now” button, it may show an error that says “There are no new definitions available to download for Windows Defender“.

It may be possible that the issue may have been caused due to an inconsistent WMI repository. Restarting the WMI repository should thus help resolve the issue.

Open Command Prompt as an Administrator. Type the following command and hit Enter:

winmgmt /verifyrepository

If you get a message “WMI repository is not consistent“, run the following command:

winmgmt /salvagerepository

This will perform a consistency check on the WMI repository and resolve the issue. Restart your machine.

Try enabling Windows Defender now.

If you get the following message instead, winmgmt /salvagerepository is failed, ignore this message, and again run “winmgmt /salvagerepository“. This time, it should help.

This post titled Unable to turn on Windows Defender offers some additional troubleshooting suggestions, which may also interest you. You may also want to check the Windows Defender error code you receive and see if any resolution is available at Microsoft.

Read this post if your Antivirus protection has expired.

You may also want to check out these posts which help troubleshoot Windows Defender problems:

• Error 0x800106a, Windows Defender will not turn on
• This program’s service has stopped – Error Code 0x800106ba
• Windows Defender Error Code 0x800106ba: Application failed to initialize
• Windows Defender Error: MSASCui.exe – Unable To Locate Component
• Error 0x80070422 The Service Couldn’t Be Started in Windows Defender
• Error 0x80508020, 0x800705b4 for Windows.
• Windows Defender Error Code 0x800106ba Application failed to initialize
• Windows Defender will not turn off even when 3rd party AntiVirus is installed
• Unable to turn on Windows Defender
• Windows Defender will not update definitions
• Windows failed to install the following update with error 0x80070643
• Windows Defender PC status – Potentially unprotected
• Error 0x80080015, The Activation Requires A Display Name To Be Present Under The CLSID Key.

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