Virus Scanner

Last reviewed 2026-08-30

Types of scans

• Quick scan — checks memory, startup items and common infection points; fast but not exhaustive
• Full scan — checks every file on every drive; slow but thorough
• Custom scan — targets a specific folder or drive, useful for checking a downloaded file or external drive
• Scheduled scan — runs automatically on a set interval without manual triggering

What a scanner is actually checking

Beyond matching file signatures, modern scanners look at registry Run keys, scheduled tasks created by unfamiliar programs, and browser extension lists — the same persistence mechanisms covered in our malware overview. A scanner that only checks files and ignores these locations will miss malware that's already survived a reboot.

Built-in vs. dedicated scanners

Windows Security includes a capable built-in scanner covering both quick and full scans. Malwarebytes Free is commonly run as a second-opinion scanner specifically because it uses a different detection engine, which occasionally catches adware or potentially unwanted programs the resident antivirus doesn't flag.

Running an effective scan

1. Update the scanner's threat database before running a full scan
2. Close unnecessary programs to speed up a full scan
3. Review every detection before deleting — some flagged items may be false positives
4. Reboot after quarantining anything tied to a startup process
5. Run a second scan after reboot to confirm nothing regenerated

Frequently asked questions

How long should a full scan take?

It depends heavily on drive size and speed, but a full scan on a typical consumer SSD often takes anywhere from twenty minutes to over an hour.

Is a quick scan good enough for routine checks?

Quick scans are reasonable for routine peace-of-mind checks, but a full scan is worth running periodically or whenever specific infection symptoms appear.

Can a scanner remove everything it detects?

Most detections can be quarantined or removed automatically, but deeply embedded threats like some rootkits sometimes require a boot-time scan or manual intervention.

Keep reading

• scanning specifically for trojansMalware that looks legitimate until it isn't.
• Malwarebytes Free as a second-opinion scannerThe limits and strengths of the free manual scanner.
• the malware categories a scanner looks forThe umbrella term for every kind of malicious software, explained.

Malware-Bytes.net is an independent information resource about malware protection for Windows. We are not Malwarebytes, and this site is not the official Malwarebytes website or support channel. Malwarebytes is a trademark of Malwarebytes Inc.