How to promote nodes/pages into blocks?
I complete the previous answer about Drupal 8.

In Drupal 8 with Views (include in core) it's exactly the same way.

Add a 'Promote to block' checkbox field on your News content type.

Then in Views you can create a new View or you can go in the "Content" View. Then create a new "Block". Describing all Views functionalities would take a long time, but in this block you can filter all your content, particularly in the Filter Criteria sections where you can filter in order to take only News content type with only the 'Promote to block' option checked.

If needed, search for some Views tutorials. It's quite easy and very powerful.

Then call this new block instead the old one.