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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchIf you suspect a rootkit on a supported Windows PC, run Microsoft Defender Offline from Windows Security. It restarts the computer and scans from a trusted environment outside normal Windows, where a rootkit has less ability to hide. A clean scan is not proof that a system is safe: rootkits can interfere with information reported by a running operating system. If detections or other credible signs of infection persist, Microsoft recommends reinstalling Windows and security software, then restoring your files from backup.
What a rootkit scan can—and cannot—tell you
Rootkits are designed to conceal malware and can intercept or alter normal operating-system processes. That means a process list or security scan running inside Windows may not show the whole picture. Microsoft warns that after a rootkit infects a device, you cannot trust information the device reports about itself. Its Sysinternals documentation similarly says there is generally no sure-fire way to confirm a rootkit from within a running system: a kernel-mode rootkit may compromise the results returned by operating-system APIs. See Microsoft’s rootkit guidance and Sysinternals RootkitRevealer documentation.
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Scanning outside the normal Windows environment is more reliable because Windows does not load in the usual way, but no scan result should be treated as an absolute guarantee. Slowdowns, pop-ups, and unexpected redirects can be reasons to scan for malware; they are not, by themselves, proof of a rootkit. Microsoft lists these as possible signs of malware generally, not rootkit-specific symptoms.
Run Microsoft Defender Offline
Microsoft Defender Offline restarts the PC into a trusted environment and scans without loading the normal Windows kernel. Microsoft describes it as a way to target persistent malware, including rootkits and infections affecting the master boot record (MBR). The built-in Windows Security route is the simplest option when it is available.
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Before you start
- Save open documents and other work. The scan restarts the computer.
- Check that your Windows edition and device are supported. Microsoft’s documented scan excludes ARM versions of Windows 10 and Windows 11, as well as Windows Server SKUs; check the current Defender Offline requirements for supported versions.
- If the system drive is protected by BitLocker, suspend BitLocker protection or make sure you have the recovery key available. Microsoft warns that you may be asked for it after the restart.
Start the scan from Windows Security
- Open Windows Security.
- Select Virus & threat protection, then Scan options.
- Choose Microsoft Defender Offline scan and select Scan now.
- Allow the computer to restart and complete the scan. Do not interrupt the restart or scan.
Microsoft’s directions are in its Defender Offline documentation and Windows Security support page.
Check the result
After Windows starts again, open Windows Security > Virus & threat protection > Protection history. Review the threat name and the action taken. If Windows Security reports a threat, follow its quarantine or removal instructions; do not assume a detection was removed unless the recorded action says so.
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When to use bootable scan media instead
If Windows cannot launch Defender Offline, Microsoft also documents creating removable offline-scanning media on a clean computer. This is an alternative, not a required step when the built-in scan works. The USB creation process reformats the drive, erasing its contents, so copy any needed files elsewhere first. Follow Microsoft’s current instructions for creating and using Defender Offline media; avoid relying on older media directions without checking that they still apply to your device and Windows version.
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| Approach | Best fit | Important checks |
|---|---|---|
| Defender Offline from Windows Security | Windows can start and the offline scan option is available. | Confirm the Windows version and architecture are supported; save work and prepare for a possible BitLocker recovery-key prompt. |
| Bootable offline media | The installed Windows environment cannot launch the built-in scan. | Create it on a clean computer and use a USB drive whose contents can be erased. Follow Microsoft’s current media instructions. |
If the scan finds nothing—or the problem continues
A scan that reports no threat does not establish that a system is clean, particularly when the scan ran from within a potentially compromised environment. Even offline scanners can potentially be targeted. If credible infection indicators or detections persist after scanning, Microsoft recommends reinstalling the operating system and security software, then restoring data from a backup. This is an escalation for a continuing problem, not a conclusion to draw from generic symptoms alone.
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Microsoft Safety Scanner is another manually run Windows malware scanner, but it is supplementary rather than proof that a rootkit has been removed. Microsoft says each download expires 10 days after download and recommends getting the latest version before each scan. The available Microsoft guidance does not establish that this tool alone resolves every rootkit or firmware-level infection. Details are on the Microsoft Safety Scanner download page.
Reduce the risk of another infection
- Keep Windows and installed apps up to date.
- Be cautious with suspicious websites, links, and email attachments; Microsoft recommends educating users about these risks.
- Back up important files regularly. Microsoft’s rootkit guidance recommends the 3-2-1 approach: keep three copies of important data, on two types of storage, with one copy stored off-site.
Backups are most useful when they are available independently of the affected PC and can be restored after reinstalling the operating system.
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- SECURE CONNECTIONS – Just a few easy clicks, and we'll automatically protect your info on public Wi‑Fi, every time you connect.
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What about macOS, Linux, or phones?
The steps above are for supported Windows devices. The cited Microsoft guidance does not establish a reliable rootkit-checking or removal procedure for macOS, Linux, Android, or iOS. Use instructions from the relevant platform’s official security support rather than applying Windows scan steps to another operating system.
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