Microsoft has made available the February 2013 system update for Xbox LIVE, which brings an update to default settings that are only visible to certain users in the EU. Other than that, there are no big changes to be seen.
According to Microsoft's Larry Hryb, "Xbox LIVE System update out today. No big changes just an update to default settings that will only be visible to certain users in the EU." In order to snag the update, you need to be logged into Xbox Live. The update only takes a few minutes to install. Have you noticed anything different after installing the update?
On a side note, it appears that someone has posted "specifics" about this update on Wikipedia (which we cannot confirm), noting a new dashboard style and other security updates. Anti-Piracy 3.0 and XGD 4.5 Challenge responses being updated as well. No official word if this is true. So keep that in mind.