電腦經常彈出"Windows Security Alert"

電腦經常彈出"Windows Security Alert"
NOTICE: If your computer is infected, you could suffer data loss, eratic PC behavior, PC freezes and crashes. Detected and remote viruses before activated on your PC to prevent all these problems.
Do you want to install AVSystemCare to scan your PC malware now?(Recommended)
如果按是便會彈出一個視窗，要dowloand某個exe.在我的電腦。
請問這個是否惡意病毒，或是Window正常的function呢？