A factory reset will remove 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 viruses can hide in the firmware — the permanent software that runs before your operating system loads — and survive a factory reset. For most people, a factory reset is effective enough to get rid of an infection, but it is not a may provide.
The reason a factory reset works is straightforward: viruses need to run from somewhere on your device. When you erase everything and reinstall the original operating system, you remove the places where those viruses were hiding. But the process takes time and you lose all your personal files unless you back them up first. Understanding what a factory reset actually does, and what it does not, helps you decide whether it is the right step for your situation.
Key Takeaways
- A factory reset removes nearly all viruses because it erases the files and programs where they hide, but firmware-level infections can sometimes survive.
- You will lose all your personal files, photos, documents, and installed programs unless you back them up to an external drive or cloud storage first.
- Before you reset, disconnect from the internet to prevent the virus from downloading more malicious files while the reset is in progress.
- After the reset completes, install antivirus software and avoid the websites or downloads that infected your device in the first place.
What happens to files and programs during a factory reset
When you perform a factory reset, the device erases the entire storage drive and reinstalls a clean copy of the operating system. This includes every file you created, every program you installed, and every virus that was running from those locations. Viruses typically live as executable files, hidden folders, or malicious code embedded in legitimate-looking programs — all of which get deleted in the process.
The operating system itself is restored to the version that came with the device, without any modifications a virus might have made to system settings or hidden files. This is why a factory reset is so effective for removing the common types of malware: ransomware, spyware, trojans, and worms all depend on files that exist somewhere on your device, and a factory reset removes them all.
Firmware infections and why they are rare
Firmware is the permanent software stored in a chip on your device's motherboard. It runs before the operating system even loads, which means it is not erased during a normal factory reset. A virus that infects the firmware could theoretically survive the reset and reinfect your device after the operating system is restored.
In practice, firmware-level infections are extremely rare. They require sophisticated code, access to specialized tools, and knowledge of your specific device's hardware. Most viruses are designed to spread quickly and widely, not to hide in firmware where they are harder to deploy. Consumer antivirus software and security researchers focus on file-based threats because that is where the real-world risk lives. Unless your device was targeted by a state-sponsored attack or a highly specialized criminal group, a firmware infection is not a realistic concern.
How to back up your files before resetting
Before you start a factory reset, decide which files you want to keep. Connect an external hard drive or USB flash drive to your device and copy over your documents, photos, videos, and any other personal files. Do not back up executable files (.exe, .app, .apk) or program installation files, because these might contain the virus. Stick to data files: photos, documents, spreadsheets, and videos.
Alternatively, you can upload files to cloud storage like Google Drive, OneDrive, or Dropbox. This method is slower but does not require a physical drive. Make sure you are uploading from a browser, not from a synced folder on your device, because a synced folder might back up infected files automatically. After the reset is complete and your device is clean, you can download these files back onto the device.
Steps to perform a factory reset safely
The exact steps depend on whether you have a Windows computer, Mac, iPhone, iPad, or Android device. On Windows, go to Settings > System > Recovery and select Reset this PC. On a Mac, restart the device while holding Command and R to enter Recovery Mode, then choose Erase Mac and reinstall macOS. On iPhone or iPad, go to Settings > General > Transfer or Reset and choose Erase All Content and Settings. On Android, go to Settings > System > Reset Options and choose Erase All Data.
Before you start, disconnect from the internet or put the device in airplane mode. This prevents the virus from downloading additional malicious files while the reset is running. The reset process can take anywhere from 30 minutes to several hours depending on your device. Do not interrupt it or turn off the device while it is running. After it completes, the device will restart and ask you to set it up again as if it were brand new.
What to do after the reset is complete
Once the factory reset finishes and your device is set up again, install antivirus or security software before you do anything else. On Windows, Windows Defender (built into Windows) is sufficient for most people, but you can also install Malwarebytes or Bitdefender. On Mac, built-in protections are generally adequate, though some people add Malwarebytes as an extra layer. On iPhone and iPad, Apple's built-in security is strong enough that additional antivirus apps are not necessary. On Android, Google Play Protect is built in, but you can also install Malwarebytes.
Restore your backed-up files from the external drive or cloud storage. Install only the programs you actually use, and download them from official sources: the Microsoft Store for Windows, the App Store for Mac and iPhone, and Google Play for Android. Avoid downloading programs from third-party websites or clicking links in emails, because these are common infection routes. If you restore files from cloud storage, do it after antivirus software is installed and running.
When a factory reset might not be enough
If your device gets infected again shortly after a factory reset, the virus is probably coming from your behavior or your accounts, not from the device itself. This happens when you restore files that contain malware, download infected programs, or visit websites that exploit security vulnerabilities. It can also happen if your email account or online accounts have been compromised — a hacker can use a compromised account to send you malicious links or files.
In these cases, a factory reset alone will not solve the problem. You need to change your passwords for email and other important accounts, scan any files you restore for viruses before putting them back on the device, and be more careful about what you download and where you download it from. If the infections keep happening, consider whether you need to update your device to a newer operating system version, because older versions may have security vulnerabilities that newer malware exploits.
Frequently Asked Questions
Will a factory reset remove ransomware?
Yes. Ransomware encrypts your files and demands payment to decrypt them, but the ransomware itself is a program that lives on your device. A factory reset erases the ransomware program, though it does not recover your encrypted files. You will need to restore from a backup made before the infection occurred. This is why regular backups are important — they protect you against ransomware even if your device gets infected.
Can I factory reset my device if it will not turn on?
Yes, but the process is different. On Windows, you can restart the device and press F8 or F11 repeatedly to enter recovery mode, then choose the reset option. On Mac, restart while holding Command and R. On iPhone, you can connect it to a computer with iTunes or Finder and restore from there. On Android, restart into recovery mode by holding Power and Volume Down together, then select the wipe option. If you are not comfortable with these steps, take the device to a repair shop.
Do I need to factory reset if I have antivirus software?
Not necessarily. If antivirus software detects a virus and removes it, the threat is gone and you do not need to reset. However, if the antivirus software cannot remove the virus, or if you are not sure whether the virus is completely gone, a factory reset is a reliable way to be certain. Some people factory reset anyway just to be safe, even if antivirus software says the threat is removed.
Will a factory reset remove spyware that is monitoring my activity?
Yes. Spyware runs as a program on your device, so a factory reset erases it. However, if spyware was installed because someone has physical access to your device or knows your passwords, they could reinstall it after the reset. Changing your passwords and securing your device against unauthorized access is just as important as removing the spyware itself.
How long does a factory reset take?
Most factory resets take between 30 minutes and two hours, depending on the device and how much data is being erased. Older devices or devices with large storage drives may take longer. Do not interrupt the process or turn off the device while it is running, because this can leave the device in an unusable state. Plan for at least an hour and make sure your device is plugged in if it is a laptop or tablet.