What to Do If You Think Your Computer Has a Virus

Pop-ups, strange browser behaviour, unexpected programs or warnings can make it feel obvious that a computer has a virus. Sometimes that is exactly what is happening. Other times, the warning itself is the scam.

First: do not call a phone number from a pop-up

Fake security alerts often claim Microsoft, Apple or another company has detected a serious problem and tell you to call immediately. Legitimate browser warnings do not normally require you to ring a support number shown in a random web page.

If you gave someone remote access or banking details: stop interacting with them, disconnect the computer from the internet if practical, and contact your bank using its official phone number if financial information may be at risk.

Common warning signs

Browser tabs or advertisements opening unexpectedly.
Your search engine or homepage changing without permission.
Security software being disabled.
Programs appearing that you do not remember installing.
Unusual account login alerts.
The computer suddenly becoming extremely slow alongside other suspicious behaviour.

Run a reputable security scan

Windows includes built-in security tools that are suitable for many everyday situations. Make sure security definitions are up to date and run a scan. Avoid downloading several random “virus remover” tools from advertisements or pop-ups.

Change passwords from a trusted device if necessary

If you believe passwords may have been exposed, use another known-clean device to change important passwords. Start with your email account because access to email can often be used to reset other accounts.

Turn on multi-factor authentication

Where available, multi-factor authentication adds another layer of protection even if a password has been compromised.

Do not rush to wipe the computer

Reinstalling Windows can sometimes be appropriate, but it is not always the first or only option. Important files should be considered before destructive steps are taken.

When to get help

If you are unsure whether the warning is genuine, someone has had remote access to the computer, malware keeps returning, or you are worried about important files and accounts, it is worth having the machine checked properly.

For small-business environments, see our business cyber security and backups.

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