Just as people catch a cold, computers can catch a virus — a harmful program. This chapter explains the kinds of harmful software (malware) and, most importantly, how to protect yourself.
1Viruses & types of malware
A computer virus is a harmful program that attaches itself to files and spreads, damaging data or disrupting the computer. (Some say VIRUS stands for Vital Information Resources Under Siege.) Viruses are one type of malware (malicious software):
| Malware | What it does |
|---|---|
| Virus | Attaches to a file; spreads when that file runs; damages data |
| Worm | Spreads by itself across networks — no host file needed |
| Trojan Horse | Pretends to be useful software but harms you once run |
| Spyware | Secretly watches you and steals information |
- A virus attaches to files and spreads, damaging data; it's a type of malware.
- A worm spreads by itself; a trojan pretends to be useful but harms you; spyware secretly steals information.
- A virus needs a host file and a user to run it; a worm doesn't.
2Symptoms & how they spread
Signs a computer may be infected:
- Runs much slower than usual or crashes often.
- Strange pop-ups, messages or new programs you didn't install.
- Files go missing, change or won't open.
- Antivirus or settings get turned off by themselves.
How malware spreads
| Route | Example |
|---|---|
| Email attachments | Opening an infected file from an unknown sender |
| Infected storage | Plugging in an infected pen drive |
| Unsafe downloads | Downloading from untrusted websites |
- Symptoms: slowdowns/crashes, strange pop-ups or unknown programs, missing/changed files, settings disabled.
- Malware spreads via email attachments, infected storage drives, and unsafe downloads.
- Never open attachments or plug in drives from unknown sources.
3Antivirus & prevention
Antivirus software protects a computer by scanning files, detecting known malware (from its virus database) and removing or quarantining it. Examples: Windows Defender, Avast, McAfee, Norton, Quick Heal, Kaspersky.
Prevention best-practices
- Install and update antivirus; keep the OS & apps updated.
- Don't open unknown email attachments or links.
- Scan pen drives before use; download only from trusted sites.
- Use strong passwords and a firewall; back up important files.
- Antivirus software scans, detects and removes/quarantines malware using its virus database.
- Keep antivirus UPDATED — new viruses appear daily and only an updated database catches them.
- Prevent infection: avoid unknown attachments, scan drives, download from trusted sites, and back up files.
★ Practical: stay virus-safe
Answer in your own words:
- Give one difference between a virus and a worm.
- List three symptoms that a computer might be infected.
- Name one antivirus program and say why it must be updated.
- Write three habits that prevent malware infections.
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