Why this matters
Windows already ships with strong security tools — Defender antivirus, SmartScreen, Tamper Protection, User Account Control (UAC) and automatic updates. The problem is that malware, fake-support scammers and 'PC optimiser' apps often disable or weaken these tools so they can keep running.
This guide walks you through turning every one of them back on and configuring them so they cannot be silently switched off again.
Step 1: Re-enable Windows Defender real-time protection
Open Settings → Privacy & security → Windows Security → Virus & threat protection, then click Manage settings under 'Virus & threat protection settings'.
Turn on every toggle: Real-time protection, Cloud-delivered protection, Automatic sample submission and Tamper Protection.
Important
If any toggle is greyed out, a third-party antivirus or a malicious 'security' app is blocking it. Uninstall unfamiliar antivirus tools from Settings → Apps before continuing.
Step 2: Turn on Tamper Protection
Tamper Protection stops malware (and dodgy 'optimiser' apps) from disabling Defender behind your back. It is the single most important toggle on this page.
It lives in the same screen as Step 1 — make sure Tamper Protection is set to On.
Step 3: Turn on SmartScreen for apps and Edge
Go to Windows Security → App & browser control → Reputation-based protection settings.
Enable: Check apps and files, SmartScreen for Microsoft Edge, Phishing protection, Potentially unwanted app blocking (both 'Block apps' and 'Block downloads'), and SmartScreen for Microsoft Store apps.
Tip
The 'Potentially unwanted app blocking' setting is what stops fake PC cleaners, fake driver updaters and bundled adware from installing in the first place.
Step 4: Set User Account Control (UAC) to its highest level
Press Win + R, type
useraccountcontrolsettings and press Enter.Drag the slider to the top (Always notify). This forces a confirmation prompt every time anything tries to change your system — including malware.
Step 5: Turn on automatic Windows Updates
Go to Settings → Windows Update. Click Check for updates, install everything offered, then click Advanced options and turn on Receive updates for other Microsoft products and Get me up to date.
Most successful Windows attacks exploit bugs that Microsoft patched months earlier. Automatic updates close that window.
Step 6: Run a final Defender scan
Go back to Virus & threat protection, click Scan options, choose Microsoft Defender Antivirus (offline scan) and click Scan now. Your PC will reboot and scan before Windows fully loads, which catches threats that hide while Windows is running.
Good to know
Combine this with a Malwarebytes Free scan for the most thorough cleanup. The two tools find different things.
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JD
Written by
Jordan DicksonFounder, CyberSecurityGuides
Founder of CyberSecurityGuides, writing practical, jargon-free guides that help everyday people recover from and protect against online attacks.
Reviewed by CSG Security Engineers