Windows 7: MSE Updates

Is it an actual MSE software upgrade or simply a definition update? I've noticed that MS releases a new definition update daily around 4a EST.

Is it an actual MSE software upgrade or simply a definition update? I've noticed that MS releases a new definition update daily around 4a EST.

Microsoft has confirmed an issue with Microsoft Security Essentials that can occur when some PCs are regularly offline for extended periods and are frequently toggled between sleep/hibernate and active mode. In some cases, these machines may be delayed in receiving their regularly scheduled signature updates.

Microsoft is aware of the problem and is working on a solution.
...

The Microsoft Antimalware group deploys updates for MSE (also Forefront and Windows Live OneCare) typically a few times daily. It is not critical for you to check for updates throughout the day because when MSE checks for updates, the offered updates will be downloaded and added to the database.

MSE will report that it is up to date and in good status even if the definitions are a few days old on the PC. Note that MSE uses the local signatures for common protection, but it also employs behavioral detection. If suspicious activity is detected, MSE will communicate with the servers to determine if a match has been reported and will immediately download any information needed to deal with the threat if a match is found.

Updates are a once per 24 hour check on a schedule determined by MSE. There is no setting within MSE to change the scheduled time or frequency.

Optionally, you can add a check for updates by setting check for updates before scan and setting up a scheduled scan daily (for a time when the PC will be on as it won't run a missed scan later).

MSE will also check 10 minutes or so after boot or wake from sleep if there is a
network connection *and* the current updates are greater than 24 hours old.
It will *not* perform this catch up check if the current definitions were installed within the past 24 hours, but will wait until the next scheduled check time.

** This "catch up" check is apparently not always working for people on wake
from sleep/standby/hibernate. Microsoft is aware of this problem and are working to fix this in a future release. So, if the PC happens to be asleep when the scheduled check is supposed to happen, and you don't have the extra check enabled, and you don't reboot, you can have older definitions. In some cases, several days old.