How to tell if your computer has been hacked
A hacked computer usually shows itself through slowness, unexpected pop-ups, changed settings, or programs you did not install. Your browser homepage might change without your action, or you might see toolbars appear that you never added. If your antivirus software is disabled, your mouse moves on its own, or you cannot log into your accounts even with the correct password, those are strong signs someone else has control.
The most reliable indicator is a sudden change in how your machine behaves — not a gradual slowdown over months, but something that happened in days or after you clicked a link or downloaded a file. Pay attention to what changed and when, because that timing tells you what to look for.
Key Takeaways
- Unexpected slowness, new toolbars, changed browser settings, and disabled antivirus are common signs of a compromised computer.
- Check your running programs, browser extensions, and installed software for things you do not recognize, because hackers often leave tools behind.
- Change your passwords from a different device while your computer is offline, because keyloggers can capture what you type.
- Run a full antivirus scan in Safe Mode to remove malware, but be prepared that some infections require professional removal.
- If you cannot regain control or suspect financial accounts are compromised, contact your bank and consider taking the computer offline entirely.
Unexpected slowness and freezing
A hacked computer often runs slowly because malware consumes processing power and memory in the background. This is different from the gradual slowdown that happens over years as your hard drive fills up. If your computer suddenly became sluggish in a matter of days, and restarting did not help, malware is a real possibility.
Open your Task Manager (press Ctrl+Shift+Esc on Windows, or Activity Monitor on Mac) and look at the CPU and memory columns. If something is using 80 percent or more of your resources and you do not recognize the program name, that is a warning sign. Malware often hides under names that sound like system processes — look for anything slightly misspelled or unfamiliar.
Browser changes you did not make
Your homepage, search engine, or new tabs changing without your action is one of the clearest signs of a browser hijack. Open your browser settings and check what your homepage is set to — if it is not what you remember, someone changed it. Look at your search engine setting too; if searches are going through an unfamiliar site, that is malware at work.
Check your installed extensions or add-ons. On Chrome, go to Settings > Extensions; on Firefox, go to Add-ons > Extensions. Remove anything you do not recognize or remember installing. Hackers often inject toolbars and search redirects this way, and they persist even after a restart because they are built into your browser.
Programs and files you do not recognize
Look at your installed programs list. On Windows, go to Settings > Apps > Apps and Features. On Mac, open Applications in Finder. Scroll through and note anything you did not install yourself. Malware often uses names that sound legitimate — "System Update," "Security Tool," "Driver Manager" — but if you did not read it, it should not be there.
Check your Downloads folder and Desktop for files you do not remember downloading. Hackers sometimes leave backdoors or tools in plain sight because most people do not look. If you see executable files (.exe, .bat, .scr) that appeared recently and you did not put them there, do not click them — that is how the infection spreads.
Disabled antivirus and firewall
If your antivirus is turned off and you did not turn it off, malware disabled it to avoid detection. Check your antivirus software and confirm it is running and up to date. If it will not turn back on, or if it keeps turning itself off, you have an active infection that is fighting back.
The same applies to Windows Defender (built into Windows) and your firewall. Go to Settings > Update and Security > Windows Security and check that Virus and Threat Protection is on. If it is grayed out or you cannot enable it, malware is blocking you. This is a sign you need to move to the next step — removing the infection — rather than just investigating.
What to do if you find signs of a hack
First, change your passwords from a different device — a phone, tablet, or another computer — while your hacked computer is offline. Do this for email, banking, social media, and any account that holds sensitive information. Use a completely different password for each account, and do not use your hacked computer to do this, because malware like keyloggers can capture everything you type.
Next, run a full antivirus scan in Safe Mode. Restart your computer and hold F8 (or Shift+F8 on newer Windows) during startup to enter Safe Mode, where only essential programs load. Open your antivirus software and run a full system scan. This can take an hour or more, but it gives the antivirus the best chance to find and remove malware without interference.
If the scan finds and removes threats, restart normally and run the scan again to confirm they are gone. If your antivirus cannot remove the infection, or if your computer still behaves strangely after removal, the malware may be too deep for consumer antivirus to handle. At that point, consider taking the computer to a repair shop or wiping it entirely and reinstalling Windows.
When to contact your bank and other services
If you entered banking information, credit card numbers, or passwords while the computer was hacked, contact your bank when ready — not through your computer, but by phone using the number on the back of your card. Tell them you suspect your information was compromised and ask them to watch for unauthorized transactions. Many banks can freeze accounts temporarily or issue new cards.
Check your credit reports through AnnualCreditReport.com (the official free source) to look for accounts you did not open. If you see fraudulent activity, file a report with the Federal Trade Commission at IdentityTheft.gov. These steps create an official record that protects you if someone tries to use your stolen information.
If you used the same password on multiple sites, change it everywhere — email, social media, shopping sites, work accounts. Hackers often try stolen passwords on many services, so one compromised password can open multiple doors. This is why using different passwords for each account matters; if one is stolen, the others stay safe.
Frequently Asked Questions
Can I get hacked just by visiting a website?
Yes, if the website has a security flaw or if you visit a malicious site, malware can install without you clicking anything. This is called a drive-by read. Keeping your browser and operating system updated patches these vulnerabilities, which is why updates matter even when they seem annoying.
What if I cannot turn off Safe Mode or my computer will not restart?
Some advanced malware locks you out of Safe Mode or prevents restarts. If this happens, you likely need professional help. A repair technician can boot from an external drive and remove the infection without relying on your compromised operating system.
Is it safe to keep using my computer after removing malware?
If antivirus removed the infection and your computer behaves normally afterward, it is usually safe to continue. However, if you entered passwords or financial information while hacked, assume those are compromised and change them from another device. If the computer still acts strangely after removal, do not trust it with sensitive information.
Should I wipe my computer and start over?
If antivirus cannot remove the infection, or if you are unsure whether it is completely gone, wiping and reinstalling Windows is the safest option. This erases everything and gives you a clean start. Back up any important files first (to an external drive, not the infected computer), then reinstall Windows from official Microsoft media.
How do I prevent getting hacked in the first place?
Keep your operating system and browser updated, use strong unique passwords for each account, enable two-factor authentication on important accounts, and be cautious about what you read and which links you click. Antivirus software helps, but it is not a substitute for caution — the safest computer is one where you do not click suspicious links or read files from untrusted sources.