The Malicious software tool is part of windows updates, but it can really take a long time when it is run. When you are notified for Windows updates by the icon in the lower right hand corner you can deselect it and hide it so it won't be installed. Double click on the icon and you will see the message install updates on your computer. You can click important updates are available. Remove the check mark beside Malicious software removal tool, then right click it and select hide update. This will prevent the installation of that updat. Unfortunately one is part of the monthly Microsoft updates and you will need to do this each month.
Hope this helps!