How to Activate Windows Security on Your Device: Windows 11, 10

To activate Windows Security, open the Windows Security app from Start, select Virus & threat protection > Manage settings and switch Real-time protection to On. Nothing has to be bought or installed, because Windows Security is built into Windows 11 and Windows 10 and is on from the moment the device starts.

When the dashboard shows red or yellow marks, a setting was turned off or another antivirus took over. The sections below switch each protection back on, from the firewall to ransomware protection, and fix the app when it refuses to start.

Why Windows Security is turned off: common causes

A few quick checks save time, because most “Windows Security is off” cases have a simple cause.

• Another antivirus: if a non-Microsoft antivirus is installed and working, Microsoft Defender Antivirus switches off by design. Decide which one you want as the primary product before changing anything.
• Administrator account: changing protection settings needs an administrator account, so a standard account sees a credential prompt.
• Work or school device: settings managed by an organisation appear greyed out and cannot be changed locally.
• Windows activation is a different thing: activating Windows with a product key is a licensing check. Windows Security works the same on activated and unactivated copies.

How to activate Windows Security in Windows 11

Windows 11 keeps the app under Privacy & security in Settings, or one search away from Start.

1. Select Start, type Windows Security, and open the Windows Security app. You can also go to Settings > Privacy & security > Windows Security > Open Windows Security.
2. Select Virus & threat protection.
3. Under Virus & threat protection settings, select Manage settings.
4. Switch Real-time protection to On and accept the User Account Control prompt.
5. Return to the home page and check that every area carries a green check mark.

A red cross means something needs immediate attention. A yellow exclamation mark is a recommendation, not a failure.

How to activate Windows Security in Windows 10

The app and its toggles are the same in Windows 10; only the Settings route differs.

1. Select Start > Settings > Update & Security > Windows Security.
2. Select Open Windows Security.
3. Select Virus & threat protection > Manage settings.
4. Switch Real-time protection to On.
5. Go back to the home page and clear any remaining red or yellow marks.

Windows 10 has no Phishing protection switch under App & browser control; everything else in this guide applies to both versions.

What is Windows Security

The app is a dashboard over several separate protections. Each one has its own page and its own on switch. On older Windows 10 builds the same app was named Windows Defender Security Center, so guides using that name describe this dashboard.

Area	What it covers	Where the switch lives
Virus & threat protection	Scanning and live blocking by Microsoft Defender Antivirus	Manage settings > Real-time protection
Firewall & network protection	Network traffic on the domain, private and public profiles	Pick a profile > Microsoft Defender Firewall
Account protection	Microsoft account sign-in status, Windows Hello and Dynamic lock	Links into the Settings app
App & browser control	SmartScreen reputation checks on apps, files and sites	Reputation-based protection settings
Device security	Hardware-backed protection reported by the device, such as device encryption	Device security page
Device performance & health	A health report for the device	Device performance & health page
Family options	Family safety settings for other accounts in the household	Family options page
Protection history	A record of recent detections and the action taken	Protection history page
Settings	Security providers, notifications and the app version	Settings > Manage providers

Open Windows Security pages directly with windowsdefender links

Each page of the app has its own address, which is handy when a toggle is buried a few clicks deep.

1. Press Windows logo key + R to open the Run dialog box.
2. Type windowsdefender://threat/ and press Enter to open Virus & threat protection.
3. Use windowsdefender://threatsettings/ for the protection toggles, windowsdefender://account/ for account protection, or windowsdefender://smartscreenpua/ for reputation-based protection.

These are the same links Microsoft’s own support pages use, so they work on current Windows 11 and Windows 10 builds.

How to enable Microsoft Defender Antivirus and real-time protection

Real-time protection is the setting that actually blocks malware as it arrives. The other switches on the same page widen what Microsoft Defender Antivirus can see.

1. Open Windows Security and select Virus & threat protection.
2. Under Virus & threat protection settings, select Manage settings.
3. Switch Real-time protection to On.
4. Switch Cloud-delivered protection to On.
5. Switch Automatic sample submission to On.
6. Switch Tamper protection to On so other apps cannot change these settings.

If real-time protection was switched off by hand, Windows turns it back on automatically after a short while. Tamper protection has to be off before the real-time toggle can be turned off at all, which is why it is worth leaving on.

How to update Windows Defender security intelligence

Security intelligence files (often called definitions) describe the latest threats. Windows downloads them through Windows Update, but a manual check is worth doing straight after you switch protection back on.

1. In Virus & threat protection, select Protection updates under Virus & threat protection updates.
2. Select Check for updates and wait for the status to say security intelligence is up to date.
3. Go back and select Quick scan.
4. For a deeper check, open Scan options and choose a full virus scan, which checks every file and running program.

How to activate Microsoft Defender Firewall

The firewall is set per network profile, so one profile can be off while the other two look fine.

1. Open Windows Security and select Firewall & network protection.
2. Select the profile you want to change: Domain network, Private network, or Public network.
3. Under Microsoft Defender Firewall, switch the setting to On.
4. Select the back arrow and repeat for the remaining profiles.
5. Confirm no profile on the Firewall & network protection page carries a red cross.

When an app needs incoming connections, add an exception for that app rather than switching the firewall off. The steps for exceptions and Control Panel settings are in our guide on how to turn Windows Firewall on or off.

Turn on account protection and Windows Hello

Account protection is a set of links into Settings rather than a page of toggles.

1. Open Windows Security and select Account protection.
2. Under Windows Hello, follow the link into Settings and finish setting up a PIN, face or fingerprint sign-in.
3. Under Dynamic lock, follow the link into Settings and turn it on to lock the PC automatically when you step away with your paired phone.

How to enable Microsoft Defender SmartScreen

App & browser control holds real toggles. They ship on, but some installers and tweak tools switch them off.

1. Select App & browser control, then Reputation-based protection settings.
2. Switch Check apps and files to On so SmartScreen rates downloads before they run.
3. Switch SmartScreen for Microsoft Edge to On.
4. Switch Potentially unwanted app blocking to On.
5. On Windows 11, switch Phishing protection on as well.

Exploit protection on the same page already runs with preset system settings, so most people never change it. More detail on each switch is in our SmartScreen settings walkthrough.

How to activate ransomware protection in Windows Security

Ransomware protection is the one area that ships off, so a green dashboard does not mean it is running. Controlled folder access lets only trusted apps change files in protected folders.

1. Open Virus & threat protection and select Manage ransomware protection.
2. Switch Controlled folder access to On.
3. Select Protected folders to see the defaults, such as Documents, Pictures, Videos, Music and Desktop, and add any other folder you care about.
4. If a trusted app gets blocked, select Allow an app through Controlled folder access and add it.
5. Under Ransomware data recovery, sign in to OneDrive so you can restore earlier versions of files after an attack.

Check device security and core isolation

The Device security page reports hardware-backed protection rather than offering much to switch on.

1. Select Device security in Windows Security.
2. Under Core isolation, select Core isolation details and turn on Memory integrity if it is off and no incompatible driver is reported.
3. Check Security processors for the TPM status and Secure boot for its state.
4. Restart the PC if Windows asks you to after changing memory integrity.

Can I use Windows Security with another antivirus?

Installing a working non-Microsoft antivirus turns Microsoft Defender Antivirus off on its own. That is designed behaviour, not a fault to repair.

Situation	Microsoft Defender Antivirus state	What Windows Security shows
No other antivirus installed	Active mode	Microsoft Defender Antivirus is turned on under Manage providers
A working non-Microsoft antivirus, Smart App Control off	Disabled automatically	That product’s status plus a link to its own settings
Windows 11 with Smart App Control on or in evaluation	Passive mode	The other product stays the primary antivirus
The other product expires, is removed, or stops giving real-time protection	Re-enabled automatically	Defender returns as the antivirus provider
You want occasional second-opinion scans as well	Stays non-primary	Select Microsoft Defender Antivirus options below the other product’s name and turn on limited periodic scanning

Limited periodic scanning uses only a small part of Defender and cannot detect most malware, so treat it as a spot check rather than cover.

Windows Security red X and yellow warning: what to do

What you see	Do this	Why
Red cross on Virus & threat protection	Turn Real-time protection back on	Nothing is scanning files as they open
Yellow mark on Firewall & network protection	Turn the firewall on for the flagged profile	One of the three profiles is switched off
Another antivirus named as your provider	Leave it primary and turn on limited periodic scanning	Two active engines conflict and slow the device
Settings greyed out or marked as managed	Take the policy details to your administrator	A work or school policy owns the setting
The app will not open at all	Repair the app from Settings	The app registration or its system files are damaged
Protection switches itself off again	Run Microsoft Defender Antivirus (offline scan)	Some malware disables protection; an offline scan runs before Windows loads

How to check whether Windows Security is activated

A green dashboard is the first signal, but the providers page is the one that names what is actually running.

1. Open Windows Security and read the home page: green check marks mean no action is recommended.
2. Select Virus & threat protection, then under Who’s protecting me? select Manage providers.
3. On the Security providers page, under Antivirus, confirm it reads Microsoft Defender Antivirus is turned on.
4. Check that Firewall and Web protection on the same page each name a provider.
5. Open Task Manager, select the Details tab and confirm MsMpEng.exe is listed.

Check the protection state from PowerShell

One line reports the mode Microsoft Defender Antivirus is running in, which the dashboard does not spell out.

Get-MpComputerStatus | select AMRunningMode

You should see: Normal, Passive or EDR Block Mode. Any other value means antivirus protection is not running on the device.

When activation isn’t enough: the offline scan

Persistent malware can turn protection off again as soon as you turn it on. Microsoft Defender Offline scans before Windows loads, where that malware has a harder time hiding.

1. Save your open files, because the PC restarts.
2. Open Virus & threat protection > Scan options.
3. Select Microsoft Defender Antivirus (offline scan), then Scan now.
4. The PC restarts into the Windows Recovery Environment, runs the scan and restarts again when it finishes.
5. Open Protection history in Windows Security to read the results.

How to fix Windows Security not activating

Windows Security will not open or shows a blank screen

The app registration is damaged, or system files behind it are corrupt.

1. On Windows 11, open Settings > Apps > Installed apps. On Windows 10, open Settings > Apps > Apps & features.
2. Find Windows Security, open the More menu or select the app, then choose Advanced options.
3. Select Repair and reopen the app. If it still fails, select Reset.
4. Open Command Prompt as administrator and run DISM.exe /Online /Cleanup-image /Restorehealth, then run sfc /scannow and leave the window open until it reaches 100%.
5. Restart the PC and open Windows Security again.

The Security Center service is stopped

The dashboard relies on the Security Center service (wscsvc) to report the status of every protection. If it is stopped or disabled, the app shows errors or blank tiles.

1. Press Windows logo key + R, type services.msc and press Enter.
2. Find Security Center and check that its status is Running and its startup type is Automatic (Delayed Start).
3. If it is not, restart the PC first; if it still will not run, follow the steps to turn on the Security Center service.

Do not stop or edit the WinDefend, SecurityHealthService and wscsvc services while troubleshooting. Microsoft’s guidance is that changing them causes instability and breaks how other antivirus products report their status.

Virus & threat protection says it is managed by another antivirus

A non-Microsoft product registered itself as the antivirus provider, so Defender stepped aside.

1. Select Virus & threat protection and read the product named on the page.
2. Open that product and confirm its subscription is current and its real-time protection is on.
3. If you want Defender back as the primary antivirus, remove the other product through Settings > Apps.
4. Restart the PC; Defender re-enables itself once nothing else provides real-time protection.
5. Check Manage providers again and confirm Microsoft Defender Antivirus is turned on.

The toggles are greyed out or say your organization manages them

A work or school policy, a Group Policy setting, or a leftover tweak controls the setting.

1. Open Windows Security > Settings > About and note the version and policy information shown there.
2. On a work or school device, send that information to whoever administers it.
3. On a personal Windows 11 or 10 Pro PC, press Windows logo key + R, type gpedit.msc, and go to Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus.
4. Open Turn off Microsoft Defender Antivirus, set it to Not configured, select OK and restart.
5. On a personal PC with a work or school account attached, remove that account under Settings > Accounts > Access work or school, then restart and check the toggles again.

Microsoft Defender Antivirus does not start after another antivirus is removed

Defender was left in its disabled state and has not picked up the change.

1. Restart the PC first, because the switch back to active mode happens at startup.
2. Run Get-MpComputerStatus | select AMRunningMode in PowerShell and read the result.
3. Open Settings > Windows Update and install every pending update.
4. Open Virus & threat protection > Protection updates > Check for updates.
5. If the mode still is not Normal, run the DISM and SFC commands above from an elevated Command Prompt.

Best practices for stronger security

• Leave Tamper protection on so malware and tweak tools cannot quietly disable real-time protection.
• Install Windows updates promptly; security intelligence and the Defender platform update through them.
• Turn on controlled folder access and keep important files in OneDrive for version history.
• Use a standard account for everyday work so changes to protection need an administrator’s approval.
• Check the Windows Security home page now and then; the dashboard is the quickest early warning you have.

Frequently asked questions

Do I need to install Windows Security, or is it already on Windows 11 and Windows 10?

It is already there. Windows Security is built into Windows 11 and Windows 10 and protects the device from the moment it starts up. There is no download, no product key and no subscription for it.

Why should I activate Windows Security?

There is nothing to activate in the licensing sense. The question usually means protection got switched off, so the task is turning Real-time protection back on under Virus & threat protection > Manage settings and clearing any red or yellow mark on the dashboard.

How do I activate Windows antivirus?

Open Windows Security, select Virus & threat protection, select Manage settings, then switch Real-time protection to On. If another antivirus is installed and working, Microsoft Defender Antivirus stays off by design until that product is removed.

How do I activate Windows 10 security?

Go to Settings > Update & Security > Windows Security > Open Windows Security, turn on Real-time protection, then turn on Microsoft Defender Firewall for the domain, private and public profiles.

How do I know if Microsoft Defender Antivirus is actually running?

Open Virus & threat protection, select Manage providers under Who’s protecting me?, and look for Microsoft Defender Antivirus is turned on under Antivirus. MsMpEng.exe on the Details tab of Task Manager confirms the same thing.

Is ransomware protection turned on by default?

No. Controlled folder access ships off. Turn it on under Virus & threat protection > Manage ransomware protection.

Should I turn on Microsoft Defender Firewall for private and public networks?

Yes, and for the domain profile too. The firewall is configured separately for each profile, so leaving one off makes the device more open to unauthorised access on that kind of network.

Why does Windows need to be activated, and what will activating Windows do?

Windows activation is a licensing check, separate from Windows Security. It confirms your copy is genuine and unlocks personalisation settings, and you can activate Windows 10 with a product key from Settings.

Can I run Microsoft Defender Antivirus alongside another antivirus?

Only as a limited second opinion. Select Microsoft Defender Antivirus options below the other product’s name and turn on limited periodic scanning. It uses a small part of Defender and cannot detect most malware.

Is Windows Security turned on by default?

Treat Windows Security as already active and spend the time on the dashboard: clear every red and yellow mark, turn on ransomware protection, then leave Tamper protection on. A warning on the home page means a setting was changed or another product took over, and the providers page names which one.