Windows Update service is responsible for frequently updating MSE. But once it is disabled MSE won’t update anymore.
Microsoft’s idea for merging the MSE update with Windows Update is perhaps the biggest downside of MSE and the only workaround until today was to manually grab the latest virus definitions. Since MSE virus definitions are updated almost daily, the manual route was quite tiresome. This is where MSE Update Utility comes in.
MSE Update Utility is a small and easy to use tool that allows you to update Microsoft Security Essentials.