Comment 347 for bug 332945

mac_v:
Ah, I should update that screenshot. The list of updates is generated by a modified version of apt-check, a python script included with update-notifier. The modification is now able to associate each updated package with an installed metapackage (such as 'ubuntu-desktop', 'kubuntu-desktop' or 'linux-generic') or, failing that, a package name that can be installed be the add/remove application. Thus, the user will only see updates for the base OS or things they will have installed manually.

I'm told the modifications to apt-check at least will be going into karmic - what, if anything, will use them is currently up in the air.