Microsoft Security Essentials is a free anti-virus provided by Microsoft that automatically scans your computer for viruses and other malware. However, in order to be the most effective, Microsoft Security Essentials has to update its virus definitions. The virus definitions are a database of all known viruses, malware, worms, trojans and other malicious software that can exist on your Windows computer. In order to detect new viruses, Microsoft Security Essentials has to have the most current database.

By default, Microsoft Security Essentials will update the virus definitions once every 24 hours. In theory, this is an effective way of keeping your virus definitions up to date and your computer safe and secure from viruses. However, as it turns out, if your computer is powered down or not connected to the Internet, the virus definitions won’t be updated. This can be problematic, because it can mean that your virus definitions remain outdated for days, weeks or even months.
A workaround for this problem is to set up a new task scheduler in Windows to automatically update the virus definitions at a time of day when you will be using the computer. Here’s how:

Step 1

Click the Start button in Windows and search for Task Scheduler. Click on Task Scheduler or press Enter when it appears.

Step 2

In the right-hand pane of Task Scheduler, click “Create Task…” Make sure you click “Create Task…” and not “Create Basic Task…”

Step 3

Give your new taks a name. “Update MSE Virus Definitions” is a logical description.

Step 4

Click Change User or Group.

Step 5

In the box below “Enter the object name to select,” type “system.”
Click OK.

Step 6

In the last drop-down menu labeled “Configure for,” select the version of Windows you are running.

Step 7

Click the Triggers tab and then choose New… In the Edit Trigger window, choose “On a schedule” for the “Begin the task” drop-down menu. Next, choose Daily. Under Advanced Settings, check “Repeat task every” and choose 6 hours. You may have to manually type it. Choose “Indefinitely” next to “for a duration of” and check Enabled. Click OK.

Step 8

Click the Actions tab and click New… In the “Action” drop-down menu, choose “Start a program.” In the Program/script field, enter:
C:\\Program Files\\Microsoft Security\\Antimalware\\MpCmdRun.exe

Or browse to wherever this executable is located on your computer.

Step 9
In the “Add arguments” field, enter “-SignatureUpdate.” Click OK

Step 10
In the Conditions tab, check the box under Network and choose “Any connection” from the drop-down menu.

Step 11
Click OK to save the task. Now, your Windows Security Essentials will automatically update its viruse definitions at least once a day.