Automatically or manually scan files and folders on your computer for malicious software using Windows Security. If you previously used a different anti-virus, you might need to enable Windows Defender Antivirus. Select Start, type Virus and threat protection, and then select it from the results. Select Manage settings, or in previous versions of Windows 10, select Virus and threat protection settings. Switch Real-time protection to On. With this enabled, Windows Defender Antivirus actively scans and protects your computer from malware. To perform an immediate scan of your computer, return to the Virus and threat protection screen. Select Scan options, or in previous versions of Windows 10, select Run a new advanced scan. There are four types of available scans. Quick scan only searches for malware in common files and folders but takes the least amount of time. Full scan searches all files and running programs on your computer. It is the most thorough scan but might take longer than an hour to complete. Custom scan searches only locations you choose to scan. Windows Defender Offline Scan reboots your computer and searches for malware before Windows loads. This is helpful when you cannot fully remove malicious software in Windows. Select your desired scan type, and then select Scan now. If necessary, respond to any prompts to begin scanning the computer. To find the scan results if they do not immediately display, return to the Virus and threat protection screen, select Scan options, and then select Threat history. For previous versions of Windows, just select Threat history on the Virus and threat protection screen.