No checklist can guarantee a virus-free computer, but a few habits can greatly reduce avoidable risks. These twelve tips focus on safe downloads, updates, account protection, and backups—not a long list of security products.
CISA’s everyday safety guidance covers scam messages, strong passwords, extra sign-in protection, and updates. Microsoft explains scanning and protection through Windows Security. [1] [2]
1. Keep Software Updated
Allow recommended security updates for your operating system, browser, and apps. Get updates from the app or official website, not a pop-up that suddenly says a special player or cleaner is required.
2. Check Messages Before Clicking
Pause if a message creates urgency or asks for money, passwords, or a download. Contact the sender using a number or address you already trust. Do not use the contact information in a suspicious message.
3. Use Official Downloads
Use the software maker’s website or an official app store. Avoid cracked software and download sites that disguise advertisements as download buttons.
4. Leave Security Protection On
Check that your security app is active and updated. Windows includes Microsoft Defender Antivirus through Windows Security. You do not automatically need a second paid antivirus to have protection. [2]
5. Review What an Installer Adds
Read the installation options and decline extras you do not want. Do not agree to a new search engine or browser extension just to finish installing an unrelated program.
6. Review Browser Extensions
Keep only extensions you use and trust. Remove unfamiliar ones, especially if your search settings or homepage changed unexpectedly. Our toolbar removal guide explains how.
7. Use Unique Passwords
A password manager can help you use a different strong password for each account. Reusing a password lets one stolen login put other accounts at risk.
8. Turn On a Second Sign-In Check
This may be a passkey, an authenticator app, or another approved method. It helps protect accounts even if someone gets the password. Never approve a sign-in you did not start. [1]
9. Be Careful With USB Drives
Do not plug in a drive you found or received from an unknown source. On a work computer, follow your organization’s rules for removable storage. [4]
10. Keep Tested Backups
Keep copies of important files, including one offsite and one offline or protected from changes by an infected computer. Test that you can recover files. Read the 3-2-1 backup guide. [3]
11. Do Not Trust Scare Pop-Ups
A website claiming your computer has hundreds of viruses is not a trustworthy diagnosis. Do not call the number, pay, or give remote access. Close the page and check your own installed security app.
12. Ask Before Making Risky Changes
Do not switch off protection, edit the registry, or run unfamiliar cleanup commands to follow a random online fix. On a work computer, ask your IT provider before removing security tools or changing managed settings.
If You Think Something Is Already Wrong
Stop using the device for sensitive logins. If you see files being locked or suspect a work-system attack, disconnect from the network and contact IT promptly. Keep backup drives disconnected and do not restore files until the system is safe. [3]
Contact PC Ninja if you need help checking a suspicious message or computer. For regular upkeep, use our computer maintenance checklist.
Sources
Sources checked October 9, 2026. Numbered links above match these references. Buying and service recommendations are PC Ninja’s advice, not guarantees.
- [1] CISA. Secure Our World (archived guidance). Accessed October 9, 2026.
- [2] Microsoft. Virus and Threat Protection in the Windows Security App. Accessed October 9, 2026.
- [3] CISA and partner agencies. #StopRansomware Guide. Accessed October 9, 2026.
- [4] Microsoft. What is malware?. Accessed October 9, 2026.