We're comfortable with Windows Defender safeguarding our systems while we surf the web in Windows 8. However, malware can also make its way onto your system if you plug in an infected external drive or USB key. Prevent such situations from occurring by using Windows Defender to scan external storage devices.
1. Click the Settings tab in Windows Defender.
2. Select Advanced.
3. Check Scan Removable Drives.
4. Click Save changes.