To download engine and definition updates immediately for all enabled engines, in the Global Settings - Engine Options pane, in the Actions section, click Update All Engines Now.

You can also perform immediate updates on selected engines. In the Global Settings - Advanced Options pane, in the Intelligent Engine Management section, using the Engine Management drop-down list, select Manual. Next, in the Update scheduling section, select the engines to be updated, right-click, and then click Update Now. (Afterwards, if you were using the default automatic setting, restore the Engine Management setting to Automatic.)

If an update exists, Microsoft Forefront Protection 2010 for SharePoint downloads it and starts using it after the download is complete. These options are useful for quick checks for a new update between regularly scheduled updates.

If updates are already in progress and you select this option, these updates are not performed until the updates in progress complete.