Computer Virus: What it is, how it spreads, and simple steps to remove and prevent it

Computer Virus

What it is

A computer virus is malware that copies itself into other files and programs—so every infected file can spread the infection again. That’s why outbreaks snowball. Viruses can slow your PC, break apps, or hide other threats. See our computer virus guide for additional detailes.

How it spreads 

  • A game mod or “free” tool with a hidden payload

  • An email attachment that looks like an invoice or homework

  • A USB stick passed around school or the office

  • Pirated software, cracks, and “keygens”

What you might notice

  • PC suddenly slower, fans loud, apps crashing

  • Files changing size or new files you don’t recognize

  • Browser home/search changed; extra ads or redirects

  • Friends saying they got weird emails or DMs from you

Do this now if you’re worried

  1. Disconnect from the internet (pause Wi-Fi) to stop spread.

  2. Run a full system scan with trusted anti-malware; remove what it finds.

  3. Reboot and scan again; then update Windows, drivers, and apps.

  4. From a clean device, change important passwords and turn on MFA.

  5. If school/work files are infected, tell IT so they can protect others.

Prevent the next one

  • Install apps from official stores/sites only; skip cracks and keygens.

  • Keep Windows, browsers, and security tools updated.

  • Before opening attachments, check the sender and file type (.exe, .scr, .js are risky).

  • Use a password manager + unique passwords; enable MFA.

  • For USBs: scan first, don’t auto-run files.

Quick myth-busting

  • “I have a Mac/Chromebook—I’m immune.” Nope. Fewer, different threats—but still threats.

  • “I clicked once, so I’m doomed.” Not always. Act fast, scan, and update—speed matters.

  • “Antivirus slows my PC.” A lightweight tool + scheduled scans beats dealing with malware.

    Glossary (A–Z)

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