Factory reset removes most malware, but not all of it, and not always in the way you might expect

A factory reset — also called a hard reset or factory wipe — erases everything on your phone and reinstalls the original operating system. This process removes the vast majority of viruses and malware because most of them live in the apps and files you've downloaded, not in the core system itself. However, a factory reset is not a may provide cure-all. Some sophisticated malware can hide in parts of your phone's memory that a standard reset doesn't touch, and a few types of malware can even reinstall themselves if the original infection method is still active.

The reason a factory reset works for most malware is straightforward: when you reset, you're deleting the infected apps, downloaded files, and user data where malware typically hides. You're also reinstalling a clean copy of Android or iOS from your phone's manufacturer. What you're not doing is replacing the phone's firmware — the low-level software that runs before the operating system even loads. Firmware infections are rare, but they exist, and a standard factory reset won't remove them.

Key Takeaways

  • A factory reset removes the vast majority of viruses and malware by wiping infected apps and files, then reinstalling a clean operating system.
  • Some advanced malware can hide in firmware or other protected areas that a standard factory reset does not touch.
  • If malware reinstalls itself after a reset, the infection method — usually a compromised app store account or a malicious link you keep clicking — is still active.
  • Before you reset, back up any photos, documents, or other files you want to keep, because the reset will delete everything.
  • A factory reset is not a substitute for removing the app or account that caused the infection in the first place.

What a factory reset actually deletes

When you perform a factory reset on Android or iOS, the phone erases your user partition — the section of storage where your apps, photos, messages, and downloaded files live. It then reinstalls the operating system from a clean copy stored on the device. This wipes out the vast majority of malware because most viruses, spyware, and adware are installed as apps or embedded in files you've downloaded.

The operating system itself — the code that runs your phone's core functions — is replaced with an untouched version from the manufacturer. This means any malware that modified system files or hid itself in the app library gets erased. For typical infections like banking trojans, spyware apps, or adware, a factory reset is highly effective.

Types of malware a factory reset may not remove

Firmware-level malware is the main exception. Firmware is the software that runs on your phone's hardware before the operating system even loads. It controls things like the bootloader and recovery partition. A standard factory reset does not touch firmware. If malware has infected the firmware itself — which is extremely rare — a factory reset won't remove it. This type of attack requires specialized tools and is typically only seen in targeted attacks against high-value targets, not in mass malware campaigns.

Malware that reinstalls itself is more common than firmware infections but still preventable. If you reset your phone but the original infection method is still active, the malware can come back. For example, if a malicious app was installed through a compromised email account or a fake app store, and you log back into that account without fixing it, the malware may reinstall. Similarly, if you keep visiting the same malicious website or clicking the same type of malicious link, you can reinfect your phone after the reset.

SIM card malware is another edge case. Some malware can hide on your SIM card rather than on the phone itself. A factory reset won't touch your SIM card. However, SIM card malware is extremely rare in consumer devices and typically requires physical access to install.

How to back up before you reset

A factory reset deletes everything on your phone, so you should back up any files, photos, or documents you want to keep before you start. On Android, open Settings, go to System, and look for Backup or Reset options — the exact path varies by manufacturer. You can back up to Google Drive, Samsung Cloud, or another cloud service. On iOS, open Settings, tap your name at the top, go to iCloud, and turn on iCloud Backup. You can also connect to a computer and use iTunes or Finder to back up.

Back up only files and photos you created, not apps. Do not back up app data from infected apps, because you may restore the malware along with the data. After the reset, you can reinstall clean versions of your apps from the official Google Play Store or Apple App Store.

Steps to perform a factory reset on Android

On most Android phones, open Settings, scroll down to System or About Phone, and look for Reset or Factory Reset. Tap it, then select Erase All Data or Factory Reset. The phone will ask you to confirm and may require your Google account password. The reset usually takes 5 to 15 minutes. Your phone will restart several times during the process.

After the reset completes, your phone will boot into the setup screen as if it were brand new. You'll be asked to sign in with a Google account and choose which apps to install. At this point, install only the apps you actually use, and install them only from the official Google Play Store. Avoid sideloading apps from unknown sources or third-party app stores.

Steps to perform a factory reset on iPhone

On iPhone, open Settings, go to General, scroll down to Transfer or Reset, and tap Erase All Content and Settings. You'll be asked to enter your Apple ID password and confirm. The reset takes 5 to 10 minutes. Your iPhone will restart and boot into the setup screen.

After the reset, sign in with your Apple ID and restore from your iCloud backup if you created one. If you're concerned the backup itself might contain malware, you can set up as a new iPhone instead and reinstall apps fresh from the App Store. This takes longer but gives you a completely clean start.

What to do after the reset to stay protected

After your phone is reset and running clean, the next step is to figure out how the malware got there in the first place. If it was a malicious app, delete that app and don't reinstall it. If it came through a compromised email or social media account, change the password for that account from a computer, enable two-factor authentication if available, and review which apps have permission to access that account.

Going forward, install apps only from the official app store for your device — Google Play Store for Android or App Store for iPhone. Be cautious about granting permissions to apps; if a flashlight app asks for access to your contacts or location, that's a red flag. Keep your operating system updated by turning on automatic updates in Settings. Updates patch security vulnerabilities that malware exploits.

When a factory reset is not enough

If your phone keeps getting infected after a factory reset, the problem is usually not the phone itself but how you're using it. This typically means one of three things: you're logging back into a compromised account, you're reinstalling the malicious app, or you're visiting the same malicious website or link. In this case, a factory reset alone won't solve the problem. You need to identify and fix the source of the infection.

If you suspect your email account is compromised, change your password from a computer (not your phone), review your account recovery options, and check which apps have access to your email. If a specific app keeps causing problems, don't reinstall it. If you keep clicking links in messages or emails that lead to malware, be more cautious about what you click. A factory reset is a tool to clean your phone, but it's not a substitute for changing the behavior that led to the infection.

Frequently Asked Questions

Will a factory reset remove spyware that's monitoring my location?

Yes, for most spyware. A factory reset will remove location-tracking apps and spyware that runs as an app on your phone. However, if someone has access to your Apple ID or Google account, they can track your location through Find My iPhone or Google Find My Mobile even after a reset, because those are account-level features, not phone-level malware. Change your account password and review which devices are signed into your account.

Can I get malware from restoring a backup after a factory reset?

Yes, if the backup contains infected app data or if you restore to an account that's still compromised. To be safe, restore only your photos and documents, not app data. Reinstall apps fresh from the official app store. If you're concerned about your account being compromised, set up your phone as new instead of restoring from a backup.

Do I need to factory reset if I just delete the malicious app?

For most malware, deleting the app removes the infection. However, some malware can hide system-level changes or install additional files that deleting the app alone won't remove. A factory reset is more thorough. If you're unsure whether the app is completely gone, a reset is the safest option.

Will a factory reset remove malware from my SIM card?

No, a factory reset only affects your phone's storage and operating system, not your SIM card. SIM card malware is extremely rare in consumer devices. If you're concerned, contact your mobile carrier to ask whether your SIM card can be scanned or replaced.

How often should I factory reset my phone to stay secure?

You don't need to factory reset regularly as a security practice. A factory reset is a response to a specific problem — a confirmed infection or a phone that's behaving strangely. For routine security, keep your operating system and apps updated, use strong passwords, enable two-factor authentication on important accounts, and be cautious about what you download and click.