While being in the process of migrating Windows Software Update Services 3.x to Configuration Manager 2012 you have only one really supported solution, namely adding all approved software updates to Software Update Group manually. This is a lot of work when being in an environment that was operational for years and years with lots of products and approved updates. Just adding all updates isn’t an option either since all approved and declined updates are tested throughout the years. When looking on the Internet for a workaround I came across this workaround for Configuration Manager 2007.
Read the complete blog here: http://configmgrblog.com/2013/10/26/migrate-approved-software-updates-wsus-configmgr-2012/