Not every slow or misbehaving computer has a virus, but a surprising number do, and the earlier it's caught, the easier it is to fix cleanly. Here are the seven warning signs we see most often, and what each one usually means.
1. Your Computer Suddenly Becomes Slow
A machine that was fine last week and is now sluggish, especially if it's slow to start up or programs take far longer to open than usual, is one of the most common signs of malware running quietly in the background, using up processing power and memory.
2. Pop-Up Ads Everywhere
Constant pop-ups, especially ones appearing even when you're not browsing, or ones claiming you've won a prize or that your computer needs urgent repair, usually point to adware, a type of malware that generates ads for money.
3. Browser Redirects
If your browser keeps sending you to websites you didn't ask for, or your homepage or search engine has changed without you touching it, that's a strong sign something has taken control of your browser settings.
4. Antivirus Disabled
Some malware is specifically designed to turn off your antivirus software so it can operate undetected. If you open your security software and find it's switched off, and you didn't turn it off yourself, treat this as a serious warning sign.
5. Unknown Software Installed
Programs or browser toolbars appearing that you don't remember installing are a common sign of bundled malware, software that sneaks in alongside something else you downloaded.
6. Suspicious Emails Sent From Your Account
If friends or family mention receiving strange emails from you that you never sent, your email account, or the computer it's accessed from, may be compromised and being used to spread the infection further.
7. Frequent Crashes and Errors
The occasional crash is normal, but frequent freezing, unexpected restarts, or error messages that weren't happening before can mean malware is interfering with how your system runs.
What to Do If You Notice These Signs
Don't panic, but do act promptly. Avoid entering passwords or banking details on the affected computer until it's been checked. Running a full scan with your existing antivirus is a reasonable first step, but some infections are specifically built to hide from standard scans, which is where a professional check makes the real difference.