Turn On Ransomware Protection (Controlled Folder Access) in Windows Security

Turn on Windows’ built-in ransomware protection so malicious programs can’t quietly encrypt or change the files in your Documents, Pictures, and other important folders.

Why: Controlled folder access checks every app that tries to change a file in a protected folder against a list of known, trusted apps. Anything not trusted is blocked from writing to those folders — which is exactly what ransomware tries to do. It’s off by default, so you have to switch it on. The trade-off: occasionally a legitimate app you use gets blocked too, and you have to add it to the allowed list yourself.

Step 1: Turn on Controlled folder access

1. Open Windows Security (Start → type Windows Security → open it).
2. Select Virus & threat protection.
3. Scroll to Ransomware protection and select Manage ransomware protection.
4. Turn Controlled folder access to On. Approve the admin prompt if it appears.

By default this protects common folders such as Documents, Pictures, Videos, Music, and Desktop.

Step 2: Add your own folders to protect

If you keep important files somewhere other than the default folders, protect those too:

1. On the same Ransomware protection screen, select Protected folders.
2. Select Add a protected folder and browse to the folder you want covered.

You can’t remove the Windows default folders from the list, but any you add yourself can be removed later from the same screen.

Step 3: Allow an app you trust that got blocked

If a program you trust (a backup tool, a photo editor, a game saving to Documents) is blocked from saving, allow it:

1. When you see the “App is blocked” notification, note the app’s name and file path.
2. Go to Virus & threat protection → Manage ransomware protection → Allow an app through Controlled folder access. Approve the admin prompt.
3. Select Add an allowed app, then browse to and select the program.

Caution: only allow apps you genuinely recognize and trust. Adding an unknown program to the allowed list defeats the protection — that app would then be free to change your files.

FAQ

Will this slow my PC down? No noticeable impact for normal use. You’ll only see it when an unrecognized app tries to write to a protected folder, which it then blocks.

A program I use keeps getting blocked — is that a virus? Not necessarily. Plenty of legitimate apps write to Documents or Desktop and aren’t on Microsoft’s trusted list yet. Confirm it’s a program you installed on purpose, then add it via Step 3.

Does Controlled folder access back up my files? No — it prevents unauthorized changes, it doesn’t make copies. For recovery, also back up to OneDrive or another location so you can restore files if something does get through.

Sources: Microsoft Support — Virus & threat protection in the Windows Security app, Microsoft Support — Allow an app to access controlled folders, Microsoft Support — Protect your PC from ransomware