What Malware Is
Malware is a general word for software designed to do something harmful or unwanted on your computer. That can include programs that spy on what you type, display endless advertisements, use your computer’s power for someone else’s benefit, lock your files, or give an outsider remote control.
Some malware is loud and obvious, but much of it stays quiet, so no symptoms does not prove a machine is clean. Equally, many signs below have ordinary explanations, so notice patterns and stay calm.
Signs Worth Noticing
Pop-ups and Unwanted Ads
- Pop-up windows appear when you are not browsing, or on sites that normally do not show them.
- Advertisements show up in places they should not, such as the desktop or inside programs.
- Full-screen alerts claim your computer is infected and urge you to call a number or install something. These are often scams in themselves, not real warnings, as explained in the piece on tech support scams.
Browser Changes You Did Not Make
- Your home page or default search engine changed on its own.
- New toolbars or extensions appeared that you do not remember adding.
- Searches are redirected to unfamiliar pages.
Unwanted browser add-ons are a very common problem. Reviewing your browser extensions and removing ones you do not recognize is a safe step.
Slowness and Strain
- The computer became much slower fairly suddenly, rather than gradually.
- The processor, memory or disk shows heavy use in the system’s task manager, caused by programs you do not recognize.
Be careful about reading too much into this. Slowness has many common, harmless causes, covered in computer slowdowns and startup programs. A full drive, too many programs starting at boot, or an aging machine are all much more usual explanations. It is the combination of slowness with other signs that deserves attention.
Programs and Settings
- Programs you did not install appear in your list of installed software.
- Security tools have been turned off, or cannot be opened, and you did not do it.
- Files have been renamed, moved, or have strange extensions, or you cannot open documents that worked before.
- A message demands payment to unlock your files. If this happens, do not rush to pay, since payment does not guarantee anything. Disconnect the computer and see the steps below.
- Your computer restarts or crashes unusually often. This also has many non-malicious causes, including hardware or driver problems.
Account and Network Signs
- Friends report receiving odd messages that appear to come from you.
- You receive password-reset emails or login alerts you did not trigger.
- Your accounts show sign-ins from places or devices you do not recognize.
These can point to a stolen password rather than malware on your own computer, so treat them as a reason to change passwords and to check account activity.
Calm First Steps
If several signs line up, work through the following in order. Take your time, since rushing can make things worse.
- Disconnect from the network. Turn off Wi-Fi or unplug the cable. This can stop a harmful program from sending data out or receiving instructions.
- Do not enter passwords on the affected computer. If something is recording keystrokes, new passwords typed here could be captured.
- Run a full scan using the security tool built into your operating system, or one from a well-known, reputable maker. Install tools only from the maker’s official site, because fake “cleaners” are a well-known trick.
- Remove what you do not recognize. Uninstall suspicious programs and browser add-ons, using the normal process for uninstalling programs. If something refuses to go away, try again after restarting in safe mode, which loads a minimal set of software and can make removal easier. Follow your maker’s official instructions for how to enter it.
- Change important passwords from a different device you trust, starting with email and banking, and turn on two-factor sign-in if you have not already.
- Check your backups. If you have a recent copy of your files made before the trouble started, you have a safe fallback. Be careful when copying files off a suspect computer, because infected files can travel with them. Backing up your important documents, photos and similar data, but not programs, is usually reasonable. The principles in backup basics apply here.
- Consider a fresh start. If scans find problems you cannot clean, or you still do not trust the computer, saving your files and doing a clean reinstall is the most dependable fix. Planning it carefully avoids losing data, so back up first.
When It Might Not Be Malware
Plenty of ordinary problems look similar. Before concluding a machine is infected, consider:
- A recent update or newly installed program that is behaving badly.
- A nearly full drive, or a drive that is wearing out. Warnings about failing drives describe symptoms that can resemble infection.
- Too many programs starting automatically.
- Dust and heat, which cause slowdowns and noisy fans.
General troubleshooting steps can help you narrow the cause. If the symptoms are limited to one browser, that points to a browser problem rather than the whole computer.
Reducing the Chance of It Happening
You cannot eliminate the risk, but you can reduce it. Keep your system and programs updated, download only from official sources, think before opening attachments, and keep backups current. The wider set of habits is outlined in home PC security basics, and learning to spot phishing emails prevents many infections before they begin.
If you remain unsure, ask a knowledgeable friend or a reputable local professional, and be wary of anyone who contacts you first offering to fix it.