10 Signs Your Device Has Malware (And What to Do About It)

Q: Can a phone get malware just from visiting a website?

Yes. Drive-by downloads can install malware on your device simply by visiting a compromised or malicious website — no clicking or downloading required. This typically exploits vulnerabilities in your browser or operating system. Keeping both updated at all times significantly reduces this risk.

Your device has been acting strange lately. Maybe it's slower than usual, or a mysterious app appeared that you never installed. Perhaps your battery is draining faster than ever, or you keep getting redirected to odd websites you never meant to visit. These aren't random quirks — they could be signs of malware that has quietly made its way onto your phone, tablet, or computer.

Malware — short for malicious software — is any program or code deliberately designed to damage, disrupt, or gain unauthorized access to a device or network. It's one of the most widespread digital threats in 2026, affecting hundreds of millions of devices every year. The challenge is that most malware is engineered to stay hidden. By the time you notice something is wrong, the infection may already have been present for days, weeks, or even months.

This guide walks you through the 10 clearest warning signs that your device is infected with malware, what to do the moment you suspect an infection, and how to protect yourself going forward — no technical background required.

What Exactly Is Malware?

Before diving into the symptoms, it helps to understand what you're dealing with. Malware is an umbrella term that covers a wide range of malicious software categories:

Viruses — self-replicating programs that attach to legitimate files and spread when those files are shared.
Trojans — disguised as legitimate software but carry harmful payloads once installed.
Spyware — silently monitors your activity and transmits data (including passwords and banking details) to a third party.
Ransomware — encrypts your files and demands payment to restore access.
Adware — floods your device with unwanted advertisements, often while tracking your browsing behavior.
Rootkits — deeply embedded programs that hide other malware and give attackers persistent system-level access.
Keyloggers — record every keystroke you make, capturing passwords, credit card numbers, and private messages.
Worms — self-spreading malware that can move across networks without any user interaction.

Each type behaves differently, but they all produce recognizable symptoms on your device. Here are the 10 most common ones to watch for.

10 Signs Your Device Has Malware

1. Your Device Has Suddenly Slowed Down

One of the first and most common signs of malware is a noticeable drop in performance. If your computer, phone, or tablet has become frustratingly sluggish — apps take longer to open, web pages load slowly, or the entire system feels laggy — malware running in the background is a likely culprit. Many types of malware, particularly cryptocurrency miners and botnets, consume significant CPU and memory resources to carry out their tasks, leaving almost nothing for legitimate programs you're actually trying to use.

It's worth noting that normal wear and a full storage drive can also cause slowdowns, so rule out those factors first. But if the slowdown was sudden and unexplained, treat it as suspicious.

2. Pop-Ups Are Appearing Constantly

Unexpected pop-up advertisements — especially ones that appear outside of your browser, persist after you close them, or warn you about fake "virus infections" — are a hallmark of adware and scareware. Legitimate software simply does not generate unsolicited pop-up ads. If you're seeing advertisements for products you've never searched for, or alarming security warnings that seem designed to make you click a link, your device is almost certainly infected with some form of malware.

Be especially cautious about pop-ups claiming your device is infected and urging you to download a "free scanner." These are often fake alerts designed to install more malware when clicked.

3. Your Browser Keeps Getting Redirected

Browser hijackers are a category of malware on phone and desktop devices that modify your browser settings without permission. Signs include: your homepage has changed to an unfamiliar website, search queries are routed through an unknown search engine, or clicking a link takes you somewhere completely different from where you intended to go. Some hijackers are subtle, inserting sponsored links into your search results while otherwise appearing normal. Others are more aggressive, redirecting every session to a malicious site designed to steal credentials or push more malware.

4. Unfamiliar Apps or Programs Have Appeared

Scroll through your installed apps or programs. Do you see anything you don't recognize or didn't intentionally install? Malware frequently arrives bundled with other software — a phenomenon called a "drive-by download" — or is installed silently after visiting a compromised website. On Android devices in particular, malicious apps sometimes disguise themselves as utility tools, flashlight apps, keyboard apps, or games. If you spot an app you can't account for, treat it as suspicious until proven otherwise.

Smartphone displaying a security alert notification — a common sign of malware on phone — Unexpected security alerts on your phone can be one of the earliest signs of malware. Photo by RDNE Stock project on Pexels.

5. Your Battery Is Draining Much Faster Than Normal

Malware running covert background operations — whether mining cryptocurrency, uploading stolen data, or maintaining a connection to a remote command-and-control server — places a heavy load on your device's processor. On mobile devices especially, this translates directly to faster-than-normal battery drain. If your phone's battery life has dropped noticeably with no change in your usage habits, check which apps are consuming the most battery power in your settings. Any unknown process eating a disproportionate share of your battery is a red flag worth investigating.

6. Unexplained Spikes in Data Usage

Spyware, ransomware, and botnet malware all need to communicate with external servers to function. This communication uses your internet connection, which shows up in your data usage statistics. If your monthly data usage has jumped significantly without any change in how you use your device — no new streaming services, no new apps, same browsing habits — malware quietly transmitting data in the background may be responsible. Check your mobile data or router statistics for unfamiliar apps or processes consuming large amounts of bandwidth.

7. Your Device Is Overheating

A device that feels unusually hot to the touch, especially when it's sitting idle or performing light tasks, is working harder than it should be. Cryptomining malware, in particular, is notorious for maxing out CPU usage around the clock, generating significant heat. Overheating isn't just a sign of a device infected with malware — it can also accelerate physical hardware degradation over time, making it doubly important to investigate and address quickly.

8. Your Security Software Has Been Disabled

Some sophisticated forms of malware are specifically designed to disable antivirus programs and firewalls as one of their first actions after installation. This removes the one tool most likely to detect and remove them. If you open your security software and find it has been turned off, if you're unable to run a scan, or if Windows Defender or your Mac's security settings appear to have been modified without your doing, this is one of the most serious warning signs on this list. A legitimate program has no reason to disable your security software.

9. Friends Are Receiving Suspicious Messages From You

If contacts start asking why you sent them a strange link, a cryptic message, or a file attachment they weren't expecting — and you have no memory of sending anything — your device or one of your accounts has likely been compromised. Many worms and trojans gain access to your contact list and messaging apps to spread themselves further, using your identity to lower a recipient's guard. This behavior is common in both email-based and social media-based malware campaigns.

10. You're Seeing Ransomware Demands or Locked Files

The most alarming symptom of all: a message demanding payment in exchange for access to your own files. Ransomware encrypts documents, photos, and other files stored on your device, then displays a demand — usually for cryptocurrency — in exchange for the decryption key. If you reach this stage, the infection has already been in place for some time. Files may be partially or fully encrypted. This is the most visible and disruptive outcome of a malware infection, though it represents only one category among many.

What to Do Immediately If You Suspect Malware

Hacker typing on a laptop in the dark — illustration of cybercrime and malware threats — Understanding how attackers operate is the first step toward protecting your devices. Photo by Sora Shimazaki on Pexels.

If several of the signs above match what you're experiencing, don't panic — but do act quickly. Here are the immediate steps to take:

Disconnect from the internet. Switch off Wi-Fi and disable mobile data. This cuts off the malware's ability to communicate with external servers, upload stolen data, or download additional payloads. It won't undo existing damage, but it limits further harm.
Avoid entering any passwords or financial information. Until the infection is resolved, assume that anything you type may be captured by a keylogger or spyware. Do not log into banking apps, email, or social media on the infected device.
Back up critical files — carefully. If you haven't already, back up important documents and photos to an external drive or cloud service. Be cautious: if ransomware is present, backing up may also back up encrypted files. Focus on files you know are unaffected.
Do not pay ransomware demands. Security researchers and law enforcement agencies universally advise against paying ransoms. Payment does not guarantee file recovery, and it funds further criminal activity. There are often free decryption tools available depending on the ransomware strain.
Alert people in your contact list if you suspect your accounts have been used to send malicious messages or links.

How to Remove Malware: Step-by-Step

The exact process for removing malware varies depending on your device and operating system, but these steps apply broadly across platforms.

On a Windows PC

Restart in Safe Mode. Safe Mode loads Windows with only essential drivers and services, preventing most malware from running. Hold Shift while clicking Restart, then navigate to Troubleshoot > Advanced Options > Startup Settings > Restart > Safe Mode with Networking.
Run a full scan with Windows Defender or a trusted third-party tool. In Safe Mode, open Windows Security and run a full offline scan. Tools such as Malwarebytes (free version) are widely respected for their thoroughness and can be run alongside your primary antivirus.
Delete any detected threats as directed by your security software. Do not simply quarantine and leave — follow through with full removal.
Remove unfamiliar programs. Go to Settings > Apps and uninstall anything you don't recognize or didn't deliberately install.
Reset your browser settings to their defaults to clear any hijacker modifications. Most browsers have a "Reset to factory defaults" option in advanced settings.
Change your passwords from a separate, clean device once the malware has been removed.

On a Mac

Check Login Items and Extensions. Go to System Settings > General > Login Items and remove anything unfamiliar. Do the same for browser extensions.
Run a reputable Mac security scanner such as Malwarebytes for Mac (free version) or Intego Mac Internet Security.
Remove unknown applications from your Applications folder, making sure to empty the Trash afterward.
Check Activity Monitor for processes consuming unusual amounts of CPU or memory that you don't recognize.

On an Android Phone

Boot into Safe Mode by holding the power button, then long-pressing "Power Off" until the Safe Mode option appears. This disables third-party apps temporarily.
Identify and uninstall suspicious apps via Settings > Apps. Pay attention to apps with vague names, no icon, or unusually broad permissions.
Run a mobile security scanner such as Bitdefender Mobile Security or the built-in Google Play Protect.
Factory reset as a last resort. If the infection persists or was particularly severe, a factory reset wipes the device completely. Back up your data to Google Drive first, then go to Settings > General Management > Reset > Factory Data Reset.

On an iPhone or iPad

iOS is a relatively closed ecosystem that makes traditional malware less common — but not impossible, especially on jailbroken devices. If you suspect an issue:

Delete any unfamiliar apps and revoke unnecessary permissions in Settings > Privacy & Security.
Update to the latest iOS version, which patches known security vulnerabilities.
Clear your browser history and website data in Settings > Safari.
Restore from a clean backup or perform a factory reset via Settings > General > Transfer or Reset iPhone if problems persist.

Malware Protection: How to Stay Safe Going Forward

The best approach to malware protection is a combination of good habits and the right tools. The following practices significantly reduce your risk of future infection.

Keep Everything Updated

Operating system updates and app patches exist largely to fix security vulnerabilities. The WannaCry ransomware attack of 2017, which affected over 200,000 computers in 150 countries, exploited a Windows vulnerability for which a patch had been available for two months prior. Keeping your software updated is the single most effective thing you can do to reduce your attack surface.

Only Download Software From Official Sources

The majority of malware infections begin with a user downloading something. Stick to official app stores (App Store, Google Play, Microsoft Store), the official websites of software developers, and well-known, reputable platforms. Be skeptical of free versions of paid software offered on third-party sites — these are frequently bundled with malware.

Be Cautious With Email Attachments and Links

Phishing emails remain the most common delivery mechanism for malware. Before clicking any link or downloading any attachment, verify the sender's actual email address (not just the display name), hover over links to preview the destination URL, and be skeptical of any message that creates urgency ("Your account will be closed in 24 hours"). When in doubt, go directly to the website by typing the URL rather than clicking a link.

Use a Reputable Security Tool

Modern security software does far more than simple virus scanning. It monitors for suspicious behavior in real time, blocks known malicious websites, checks downloads before execution, and provides ransomware protection by monitoring for bulk file encryption. Windows Defender (built into Windows 10 and 11) is genuinely effective as a baseline. Supplementing it with a tool like Malwarebytes adds an additional detection layer, particularly for adware and potentially unwanted programs.

Avoid Public Wi-Fi Without a VPN

Public Wi-Fi networks at coffee shops, airports, and hotels are common vectors for man-in-the-middle attacks, where an attacker positions themselves between you and the network to intercept traffic or redirect you to malicious sites. Using a trusted VPN encrypts your connection and makes it significantly harder for attackers on the same network to interfere with your traffic.

Enable Two-Factor Authentication

Even if malware manages to capture your password, two-factor authentication (2FA) adds a second layer that an attacker typically cannot bypass without physical access to your phone. Enable 2FA on every account that offers it, prioritizing email, banking, and social media accounts. Use an authenticator app rather than SMS where possible, as SMS-based codes can be intercepted via SIM-swapping attacks.

Review App Permissions Regularly

Both Android and iOS allow you to review and revoke app permissions at any time. A flashlight app that requests access to your contacts, microphone, and location has no legitimate reason for those permissions. Auditing your permissions periodically is a quick and effective way to identify apps that may be collecting more data than they should.

Frequently Asked Questions About Malware

Can a phone get malware just from visiting a website?

Yes. So-called "drive-by downloads" can install malware on your device simply by visiting a compromised or malicious website — no clicking or downloading required. This typically exploits vulnerabilities in your browser or operating system, which is one more reason to keep both updated at all times. Using a browser with built-in security features and enabling pop-up blocking reduces this risk significantly.

Does malware affect iPhones?

iPhones are significantly harder to infect than Android or Windows devices due to Apple's closed app ecosystem and sandboxing model. However, they are not immune. Jailbroken iPhones lose most of these protections. Additionally, phishing attacks, malicious profiles installed via web links, and vulnerabilities in Safari can all affect iOS devices. Keeping iOS updated and avoiding jailbreaking are the most effective defenses.

Will a factory reset remove all malware?

For the vast majority of malware, yes — a factory reset wipes the operating system and all user data, removing the infection. The exception is a small category of extremely sophisticated malware called firmware-level or bootkit malware that embeds itself below the operating system. These are rare and typically associated with nation-state level attacks, not everyday consumer malware. For most users, a factory reset is an effective last-resort solution.

How long can malware go undetected?

Industry research suggests the average time between a malware infection and its detection is around 197 days. Sophisticated malware is specifically designed to avoid detection: it may lie dormant, mimic normal processes, or operate only during times when the user is unlikely to notice (such as overnight). This is why regular proactive scans — not just reactive scanning when problems appear — are an important part of good digital hygiene.

Is free antivirus software good enough?

For most home users, free tools like Windows Defender, Malwarebytes Free, and Avast Free provide a solid baseline of protection. Paid versions typically add features like real-time web protection, ransomware rollback, a VPN, and identity monitoring — useful additions for higher-risk users. The most important factor isn't free versus paid, but whether you actually keep the software updated and run regular scans.

Key Takeaways

Malware is not always dramatic or obvious. In many cases, a device infected with malware shows only subtle symptoms — a slight slowdown here, a small spike in data usage there — that are easy to dismiss as normal device aging. The 10 warning signs covered in this guide give you a practical checklist to run through whenever your device starts behaving unexpectedly.

The key points to remember:

Unexpected slowdowns, pop-ups, redirects, and unfamiliar apps are among the most common early signs of malware.
Overheating, rapid battery drain, and unusual data usage often indicate malware running hidden background processes.
If you suspect an infection, disconnect from the internet immediately and avoid entering sensitive information until the device is clean.
Most malware removal can be accomplished with a combination of Safe Mode, reputable scanning tools, and removing suspicious software.
The best malware protection is proactive: keep software updated, use strong passwords with 2FA, download only from official sources, and be cautious with email links and attachments.
A factory reset is an effective last resort for persistent infections on both mobile and desktop devices.

Staying informed about how malware behaves is one of the most practical steps any device user can take. The threats evolve constantly, but the fundamentals of good digital hygiene — skepticism, regular updates, and knowing what normal looks like on your device — remain the most reliable defenses available.