Strange pop-ups, unexpected apps and a mind-of-its-own webcam? Here’s how to tell if your computer has been hacked—and what to do about it.
How to Tell If Your Computer Has Been Hacked
Updated on Jun. 25, 2025
How do hackers get access to your computer?
Hackers have many tricks up their sleeves. Viruses and malicious software, aka malware, make the most of security gaps, but something called social engineering is even easier. As Ravichandran points out, “Hackers and scammers know there’s one vulnerability they can always exploit: you.”
Social engineering attacks use so-called human hacking to get around cybersecurity roadblocks. “Instead of hacking your accounts to steal your identity, they hack you by using phishing attacks, imposter frauds and other scams,” he says. This deceptive psychological manipulation instills fear, excitement and urgency. “Once you’re in a heightened emotional state, they’ll use that against you to cloud your better judgment,” Ravichandran adds.
Once they have you hooked, they swoop in to steal your data, personal information or banking details. If you suspect that may have happened to you, look for these subtle (and not-so-subtle) clues that your computer has been hacked.
Your computer starts running slower
If it suddenly takes forever for your computer to boot up or for applications to open, it may be infected. Viruses, Trojans and worms, which run in the background and use a lot of your computer’s memory, can really slow down your device.
Of course, computers can be slow for many reasons, including lack of maintenance, a full hard drive, overheating of the processor and more. Snail-like speed isn’t a definitive sign your machine has a bug. Still, if your computer is lagging, it’s a good idea to use security software to scan your device and remove any problematic programs. Doing so could fix the problem and make your computer run faster.
Your battery is drained, and your fans go into hyperspeed
A compromised computer is inefficient, so keep an eye on how your computer sounds and feels. “One of the simplest ways to tell if a machine or mobile device has spyware, crypto-mining malware or other viruses that consume processing power is paying attention to the physical temperature and battery life of the machine,” says Bill Siegel, founder of ransomware recovery company Coveware.
Is your computer fan running more than half the time? Is your phone or computer hot to the touch? Does your device suddenly need to be charged three or four times a day? All of these symptoms could be signs that malware is running and using significant power.
Programs automatically connect to the internet
Is your calculator app suddenly connecting to the internet? Does your media player launch without asking? Paige Hanson, co-founder of SecureLabs, and Jeff Nathan, the director of detection engineering at Netography, say these could be signs of a hacked device. Malware often has a directive to connect back to its home server, so if you’re seeing programs start connecting to the web on their own, especially ones that normally don’t, that’s a red flag.
Even programs that normally connect can be suspicious if they start behaving strangely for that application. Excessive popups, prompts to download unusual updates or connecting constantly to random servers are all clues. So, if you’re wondering how to tell if your computer has been hacked, check the task manager, and be on the lookout for programs that connect to the internet when you’re not using them.
Your webcam randomly turns on
You probably know how to browse the internet anonymously by opening an incognito browser. But it’s a good idea to hide your camera, too. Hackers can access your camera for nefarious purposes, and one way to tell it’s happening is that your camera keeps starting by itself, says cybersecurity expert and journalist David Geer. (You’ll know it’s on by the indicator light.)
Online spies aren’t necessarily trying catch you walking around naked. They’re often trying to get a peek at passwords as you type them in. While the best protection is maintaining strong digital security, you can go above and beyond by blocking their view. Place a piece of tape over your webcam when it’s not in use, or buy a special webcam cover, to protect your privacy and any sensitive information you have on your desk. Or use an external camera for meetings, then unplug it when you’re done.
You see unknown sending and receiving lights
Raise your hand if you pay attention to the lights on your router or modem. Good for you! For the rest of us, it’s smart to give them a glance every once in a while. They may tip us off that someone is controlling our computer. “Blinking ‘send’ and ‘receive’ lights when your computer is idle is a warning sign,” says Jack Vonder Heide, a tech expert and CEO of Technology Briefing Centers.
Look at your devices. They’ll have lights that are consistently lit or flashing, indicating you’re connected to the internet or receiving data. The colors will vary by brand, so pay attention to what’s normal on your modem, router and computer. That way, you’ll have an easier time spotting lights acting oddly. If you suddenly notice an increase in blinking even when you’re not online, it’s a sign of trouble.
Your apps act up
Computer apps make our lives easier, but they can also be vehicles for malicious code aimed at collecting our data. This is called an injection attack, and according to Crowdstrike, the code gives hackers the ability to execute remote commands or access data and systems. If an app is running slowly, or crashing more frequently than usual, it may be compromised.
And heads up: Bad apps don’t just live on computers; they’re found on smartphones, too. To safeguard both, make sure you’re dealing with a reputable company before downloading an app from the internet.
You notice unusually high internet data consumption
Has your internet usage skyrocketed out of the blue? You’ve probably been hacked, according to Ravichandran. Why do hackers gobble up so much data? Well, once they gain access to your computer, they know it’s only a matter of time before they’re discovered. So they aggressively go through your system to get as much data and sensitive information as possible before you take action.
Hackers might also use your system to attempt to reach and control another system, or people in your address book or on your network. Hackers can do a lot with just your cell phone number, so imagine what they could do with all of that data. Take action the minute you notice suspiciously high internet usage.
You start seeing more pop-up ads
“If all of a sudden you have browser add-ins or plug-ins you don’t remember installing, your machine may be infected,” says Richard Ford, vice president of engineering at CyberCube. “Often, these add-ins help an attacker monetize their access to your machine. Similarly, if the web now seems full of pop-up advertisements, you may be infected.”
Your smart devices act stupid
The Internet of Things (IoT) aims to make life easier. Voice assistants can play music or tell you the weather. Smart thermostats keep your environment comfortable, and smart locks secure your home. But IoT devices are “common targets for bad actors, as they don’t have space to run proper security systems, and often store sensitive information like log-in details and passwords,” Ravichandran says.
That’s right: Items in your home could be spying on you. “Once they install malware, hackers can link devices together and launch [denial of service] attacks,” he says. “These attacks attempt to knock out networks by flooding them with traffic.” Unfortunately, once hackers are in, they can gain access to your entire system. Pay attention to odd behavior like devices that turn on and off randomly, strange sounds, spikes in data usage and passwords that don’t work.
Your homepage changed
You may know all the ways Google is tracking you across the internet. But something even more nefarious may be following you: spyware. “If you open your web browser and are taken to an unfamiliar page instead of your normal homepage, or if you type a search term into your browser and another browser pops up with a list of websites for your search term, this could be a sign of spyware,” says cybersecurity consultant Stacy Clements. “This is especially true if you realize your browser settings have been modified and you are unable to change the settings.”
Mysterious tools start showing up
“Other signs of potential spyware are files appearing on your computer, or toolbars and tray icons that you didn’t install,” Clements says. Do you have a cluttered computer desktop? A non-existent file system? This would be a good time to tidy things up. A bit of spring cleaning will help you keep track of your apps and programs. If something sketchy pops up as you organize, you can take immediate action.
Websites and other tools stop responding
You open a web browser, and faster than you can search “how to tell if my computer has been hacked,” you encounter website after website that won’t load. That’s a red flag you’ve been hacked, says Trave Harmon, founder and CEO of Triton Technologies. “I’m not talking about one or two websites, but multiple ones that aren’t related,” he says.
Here’s an even bigger clue that something is afoot: Your coworkers or other people on the same network aren’t having any problems accessing these same sites. You may also find that your antivirus software or some system tools on your computer are unresponsive or don’t work properly.
You get a warning
“If an antivirus warning pops up, don’t ignore it,” says Adam Dean, an incident response and forensics lead at Octillo, a law firm specializing in data security and privacy. And don’t presume your antivirus software has removed the virus, either. “If you see a malware detection by antivirus software, assume it’s letting you know you have an issue, not that it has deleted the virus,” he says.
Be very careful when deleting so that you don’t inadvertently start the program. Follow your computer’s prompts on how to delete a program, and then empty your trash bin to be on the safe side. One note: Sometimes malware can be disguised as a warning. Hover your cursor over the link before clicking, scan the URL, and make sure it’s legit.
Passwords are not working
Google’s not working. You can’t access your Instagram account. And though you’re positive you’re using the correct password, you’re locked out of your health insurer’s site. According to Ravichandran, if none of your passwords work, especially across multiple sites all at once, you’ve probably been hacked.
Your account is sending mass emails
This situation is a bit tricky. It’s possible that your email account was hacked and not your computer. But if you notice giant group emails being sent from your account to every single person in your address book, it’s probably a sign that your computer was hacked.
What to do if you’ve been hacked
Act quickly. Someone may have access to all your information and contacts. “Once cybercriminals have remote access to your computer, the potential for identity theft and financial losses increases dramatically,” say Hanson and Nathan. The longer you wait to tackle the problem, the more time hackers have to steal your personal information and target people in your network.
Here’s what to do:
Confirm the breach
Have your computer examined for malware as soon as possible, Ravichandran says. Hanson and Nathan suggest using a different computer to schedule the appointment: “If possible, use a separate device to locate a reputable source of technical support, as some malware will prevent you from browsing a legitimate antivirus site.”
It’s important to “find out what sensitive data was stolen and is available to hackers,” Ravichandran says. Ask yourself what’s accessible on your computer: social security numbers, bank and retirement accounts, home title information, phone numbers, home address? Having this information handy will help later.
Update your passwords
“Think back to what websites you’ve visited while your computer [or] device has been compromised, and update those passwords immediately,” Hanson and Nathan advise. Using a password manager makes keeping track of hard-to-crack passwords easier, and the pair say if you’ve been hacked, it’s safer to update passwords using another device.
Then, go a step beyond basic security by setting up two-factor authentication (or multi-factor) for all your accounts.
Freeze your credit
Bad actors can use data collected from your computer to steal your identity, so it’s crucial to freeze your credit after a hack. Contact Equifax, Experian and TransUnion, and call your bank to set up a fraud alert to prevent unauthorized access or card use.
Monitor your accounts
Next, keep an eye out for suspicious activity. Monitor web activity for things like failed log-in attempts and odd emails, and check your bank account for unknown charges. Keep tabs on your credit file and credit card charges to make sure no one has opened new accounts in your name.
Sign up for identity theft prevention
Sign up for a service that monitors credit information and prevents identity theft. Ask your bank or credit card company if they have a tool to monitor the dark web for your data, or use a monitoring company like LifeLock or Crowdstrike.
How to protect your computer from hackers
The best way to avoid getting hacked is to have a solid, reputable antivirus or anti-malware program installed on your computer, says Troy Wilkinson, the CEO of Axiom Cyber Solutions. “These cost just a couple of dollars a month, so there really is no valid reason not to use one,” he says. “But if you get infected, spyware can run hidden in the background, silently collecting your information, and could cost you hundreds or thousands in the long run.”
In addition to installing antivirus software, follow these expert tips for protecting your computer from hackers and spyware:
- Never open suspicious emails or click on suspicious links
- Use strong passwords
- Don’t download pirated material
- Don’t use USB devices that aren’t yours
- Install a firewall
- Update your computer when prompted
- Use multi-factor authentication
FAQs
Can someone spy on me through public Wi-Fi?
Yes. Public Wi-Fi networks can be exploited through middleman attacks, where a hacker intercepts data between your device and the internet. Using a VPN adds a layer of encryption to help protect your activity.
Could a browser extension be used to spy on me?
Absolutely. Malicious browser extensions can log keystrokes, track browsing behavior and even inject malicious ads. Stick to well-reviewed extensions from trusted developers, and check permissions before installing.
Additional reporting by Joe McKinley.
About the experts
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Reader’s Digest has published hundreds of articles on personal technology, arming readers with the knowledge to protect themselves against cybersecurity threats and internet scams as well as revealing the best tips, tricks and shortcuts for computers, cellphones, apps, texting, social media and more. For this piece on how to tell if your computer has been hacked, Rachel Weingarten tapped her experience as an award-winning freelance writer specializing in beauty, fashion, business and tech, and then our Reader’s Digest editors gave it a rigorous review to ensure that all information is accurate and offers the best possible advice to readers. We rely on credentialed experts with personal experience and know-how as well as primary sources including tech companies, professional organizations and academic institutions. We verify all facts and data and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.
Sources:
- Paige Hanson, certified identity theft risk management specialist and co-founder of SecureLabs
- Jeff Nathan, director of detection engineering at Netography
- Hari Ravichandran, founder and CEO of Aura Identity Protection
- Bill Siegel, founder and CEO of Coveware
- David Geer, cybersecurity consultant and writer
- Jack Vonder Heide, CEO of Technology Briefing Centers
- Richard Ford, PhD, vice president of engineering at CyberCube
- Stacy M. Clements, cybersecurity consultant and owner of Milepost 42
- Trave Harmon, founder and CEO of Triton Technologies
- Adam Dean, incident response and forensics lead at Octillo law firm
- Troy Wilkinson, CEO of Axiom Cyber Solutions
- FBI: “FBI Releases Annual Internet Crime Report”
- Crowdstrike: “Seeing the Unseen: Preventing Breaches by Spotting Malicious Browser Extensions”
- Crowdstrike: “Injection Attacks”
- Federal Trade Commission: “Are Public Wi-Fi Networks Safe? What You Need To Know”
