After you have configured the on-demand scan, you can run it immediately.To run the on-demand scan immediately
In the Forefront Protection 2010 for SharePoint Administrator Console, click Tasks, and in Task Library, click On-Demand Scan.
In the Task Library - On-Demand Scan pane, in the Actions section, click Start On-Demand Scan. This sets the start time to the current time, thus starting the scan.
Note: To stop an on-demand scan that is running, click Stop On-Demand Scan. To suspend a running on-demand scan, click Suspend On-Demand Scan. To resume a suspended on-demand scan, click Resume On-Demand Scan. Clicking Resume On-Demand Scan starts a suspended scan from where it left off; however, if you click Start On-Demand Scan when a scan has been suspended, the scan starts from the beginning again.
After running the on-demand scan, you can use the Forefront Management Shell to check its status.To check scan status
Click Start, point to All Programs, point to Microsoft Forefront Server Protection, and then click Forefront Management Shell.
Enter the following Windows PowerShell command:
The status can be ACTIVE, STOPPED, or SUSPENDED. A status of ACTIVE indicates that the scan is still running, STOPPED indicates that it has completed, and SUSPENDED indicates that it was paused.