8 Signs Your Computer Has a Virus
Malware rarely announces itself with a skull on the screen. Modern infections mostly want to stay hidden — quietly showing you adverts, mining your passwords, or waiting for instructions — which means the signs are subtle and easy to blame on "the computer just being slow". Knowing what to look for is half the battle. Here are the warning signs we see most often in the workshop, what to do the moment you spot them, and how to tell a real infection from an innocent slowdown.
The warning signs
- Sudden slowdown with no obvious cause, or a fan that never stops spinning even when you're doing nothing.
- Pop-ups and adverts appearing on the desktop, or over websites that shouldn't have them.
- Your browser changed itself — a new home page, search engine or toolbar you didn't choose, or searches that go somewhere odd.
- Programs you don't recognise launching at start-up or appearing in your apps list.
- Crashes and freezes that have suddenly become frequent.
- Friends receiving odd messages from your email or social accounts — a sign your credentials are being used.
- Security software disabled or unable to update. Malware's first job is often to switch off the thing that would catch it, so this sign deserves particular respect.
- Files locked or renamed with a payment demand — that's ransomware, the most serious of the lot.
- Browser warnings about your passwords appearing in bulk, or accounts logging themselves out unexpectedly.
Slow doesn't always mean infected
Worth saying clearly: a slow computer is far more often a tired one than an infected one — a nearly-full drive, too little memory, an ageing mechanical hard drive, or an overheating machine throttling itself. Our guide to a computer running slow covers those innocent causes. What separates malware from mere age is the combination of signs: slowness plus pop-ups, browser changes, or disabled security is a very different picture from slowness alone. One sign is a maybe; three together is a scan, today.
What to do right now
- Disconnect from the internet — turn off Wi-Fi or pull the cable. This stops data leaving and prevents the infection spreading or updating itself.
- Don't log into banking or type any passwords on the machine until it's confirmed clean — if something is capturing keystrokes, every login makes it worse.
- Run a proper scan. On Windows, the built-in Microsoft Defender is a sensible first step — our guide to running a malware scan walks through it, including the offline scan for stubborn threats. Avoid the random "cleaner" tools advertised in pop-ups; many are the disease pretending to be the cure.
- Change key passwords from a different, trusted device — your phone, or another computer — starting with email, and turn on two-factor authentication while you're there.
After the all-clear: check the damage
Removing the malware is step one; step two is asking what it did while it was there. Check your email's sent folder and any forwarding rules (see recovering a hacked email), review recent bank and card activity, and watch your accounts for unfamiliar logins over the following weeks. If the infected machine was used for work, tell whoever runs your IT — quietly hoping is how one infected laptop becomes a company-wide incident.
How infections get in — close the door behind them
Malware needs an invitation, and the invitations are remarkably consistent: an email attachment or link that looked plausible (see spotting phishing), software downloaded from somewhere other than the official source, a "free" version of a paid program, a fake "update your player" pop-up, or an out-of-date system missing years of security patches. Whichever route was used this time, it stays open until it's identified and closed — which is why the same machines tend to come back infected again and again until the habit or the hole is fixed. Part of a proper clean-up is working out the "how" so there isn't a next time.
Why a proper clean-up matters
Some malware hides, reinstalls itself after removal, or leaves a back door open for a return visit — so a single scan that says "all clear" isn't always the full story. A thorough professional clean-up removes the infection, verifies nothing persists, checks what it touched, and closes the gap it came in through — whether that was a dodgy download, an email attachment, an out-of-date program or a scam phone call. And where any doubt remains, a clean install is the certain, guaranteed fix.
We'll get it clean — and keep it that way
Our computer repair team removes viruses and malware properly, confirms your data is safe, and secures the machine against a repeat — while our cyber security service puts the protection and habits in place so it doesn't happen again.