A factory reset removes most viruses, but not all of them

A factory reset wipes your device back to its original state, erasing everything you installed and all your files. This process removes the vast majority of viruses because they live in the files and programs on your device, not in the core system itself. However, some sophisticated malware can hide in the firmware — the permanent instructions built into your device's hardware — and survive a factory reset. For most people dealing with a typical virus, a factory reset will solve the problem. For targeted attacks or extremely persistent malware, it may not be enough.

The reason a factory reset works for most viruses is straightforward: viruses need to run code on your device to do damage. When you factory reset, you delete all the code that isn't part of the original system. The virus has nowhere to hide and nothing to execute. But this only works if the virus lives in the normal file system where you store documents, photos, and programs. If malware has infected the firmware layer — the instructions that run before your operating system even loads — a factory reset leaves it untouched.

Key Takeaways

  • A factory reset removes nearly all common viruses because it deletes the files and programs where viruses hide.
  • Some advanced malware can survive a factory reset by hiding in firmware, the permanent instructions built into your device's hardware.
  • Before you factory reset, back up any files you want to keep, because the process deletes everything except the original system.
  • If your device still behaves strangely after a factory reset, the virus may have been in the firmware, or the problem may not be a virus at all.

Why viruses live in files and programs, not in hardware

When you read a malicious file or install a compromised program, the virus code sits in your storage — on your hard drive, solid-state drive, or phone's memory. Every time your device runs that file or program, the virus runs too. It can steal passwords, display unwanted ads, slow down your system, or lock your files for ransom. But it is still just code stored in a location your operating system can access and delete.

A factory reset tells your device to erase everything in that storage and reinstall the original operating system from a backup copy. This is why the virus disappears. The malware has no files left to run from, and the fresh operating system has no trace of it. This works the same way on Windows computers, Macs, iPhones, and Android phones — the virus lives in the user-accessible layer, and a factory reset removes it.

When a factory reset might not be enough

Firmware is the code that runs before your operating system loads. It is stored in a special chip on your device's motherboard or logic board, separate from your regular storage. Most viruses cannot reach firmware because the operating system protects it. But a very advanced piece of malware — usually created by a government agency or a well-funded criminal group — can sometimes infect firmware directly. This type of malware survives a factory reset because the reset only touches the operating system and user files, not the firmware.

In practice, firmware-level malware is extremely rare. It requires significant resources to create and is usually aimed at specific targets like activists, journalists, or corporate executives. If you have a typical virus from visiting a malicious website or opening a suspicious email, a factory reset will remove it completely. You should only worry about firmware-level threats if you have reason to believe you are being targeted by a sophisticated attacker.

How to back up your files before factory resetting

A factory reset erases everything on your device except the operating system. Before you proceed, move any files you want to keep to an external location. On Windows, connect an external hard drive or USB drive and copy your Documents, Pictures, Downloads, and Desktop folders to it. On Mac, do the same with your Documents, Downloads, and Desktop folders. On iPhone or Android, use cloud storage like Google Drive, OneDrive, or iCloud to back up photos, contacts, and documents.

Make a list of the programs you use regularly, because you will need to reinstall them after the reset. Write down any login credentials you might have forgotten, because you will need them to sign back in to your accounts. Once your files are safely backed up and you have your list of programs, you can proceed with the factory reset.

The steps to factory reset on different devices

On Windows 10 or 11, go to Settings, select System, then Recovery. Click "Reset this PC" and choose "Remove everything." Windows will ask whether you want to remove files locally or cloud-based, and whether to reinstall Windows from the cloud or a local copy. Choose the option that works for your situation, then follow the prompts. The process takes 30 minutes to an hour.

On Mac, restart your computer and hold Command and R to enter Recovery Mode. Once Recovery Mode loads, select Erase Mac from the Utilities menu, choose your startup disk, and confirm. Then select Reinstall macOS and follow the prompts. This takes 45 minutes to two hours depending on your internet speed.

On iPhone, go to Settings, select General, then Transfer or Reset. Tap "Erase All Content and Settings" and enter your Apple ID password. The phone will reset in a few minutes.

On Android, go to Settings, select System, then Reset Options. Tap "Erase all data (factory reset)" and confirm. The process takes a few minutes. Note that the exact path varies by manufacturer — Samsung, Google Pixel, and other brands have slightly different menu layouts.

What to do if your device still has problems after resetting

If your device behaves strangely even after a factory reset, the problem may not be a virus. Slow performance, crashes, or unexpected behavior can come from a failing hard drive, overheating, outdated drivers, or software conflicts. Try running a diagnostic tool: Windows has a built-in tool called Windows Defender Offline that scans for viruses before the operating system loads. Mac has Disk Utility to check for drive errors. If these tools find nothing and the problem persists, the issue is likely hardware-related rather than malware-related.

If you suspect firmware-level malware — which is extremely unlikely unless you are a high-value target — you will need professional help. Contact the manufacturer's support team or a specialized security firm. For everyone else, a factory reset followed by careful browsing habits and updated antivirus software will keep your device safe.

How to avoid needing a factory reset in the first place

The best defense against viruses is prevention. Keep your operating system and all programs updated, because updates patch security holes that malware exploits. Use antivirus software like Windows Defender (built into Windows), Malwarebytes, or Bitdefender. Do not read files from untrusted websites, and be cautious about email attachments from people you do not know. Use strong, unique passwords for each online account so that if one account is compromised, the others remain safe.

Enable two-factor authentication on important accounts like email and banking. This adds a second verification step even if someone has your password. Avoid connecting to public Wi-Fi without a VPN, because unencrypted networks make it straightforward for attackers to intercept your data. These habits reduce your risk of infection so much that most people will never need a factory reset.

Frequently Asked Questions

Will a factory reset delete my photos and documents?

Yes, a factory reset deletes everything except the original operating system. Before you reset, back up your photos, documents, and any other files you want to keep to an external drive or cloud storage. Make a list of programs you use so you can reinstall them afterward.

Do I need to factory reset if I just have a virus warning pop-up?

Not necessarily. Many virus warning pop-ups are scams designed to scare you into clicking them. Close the browser tab or restart your device. If the pop-ups return, run a legitimate antivirus scan with Windows Defender or Malwarebytes before resorting to a factory reset. A factory reset is a last resort, not a first response.

How long does a factory reset take?

On phones, a factory reset takes a few minutes. On computers, it takes 30 minutes to two hours depending on your device and internet speed. During the reset, your device will restart multiple times. Do not turn it off or unplug it until the process finishes.

Can I factory reset my device if I forgot my password?

On Windows, you can reset a forgotten password through the login screen by answering security questions or using a recovery email. On Mac, you can use Recovery Mode and your Apple ID to reset your password. On iPhone and Android, you will need your Apple ID or Google account credentials. If you have forgotten those too, contact the manufacturer's support team for help.

What if the virus comes back after I factory reset?

If you get infected again after a factory reset, you are likely visiting the same malicious websites or downloading files from the same unsafe sources. Change your browsing habits: avoid clicking suspicious links, do not read files from untrusted sites, and use antivirus software. If the infection returns despite these precautions, the problem may be malware in your router rather than your device — contact your internet provider for help.