There is a new drop down within the project creation dialog that when selected will prevent all users from viewing the project. When the project is restricted, it is then required by a Project Manager/Admin to manually assign that project to the users who are allowed to work within that project.
To begin with every existing project that is stored in the cloud will not have the project restrict flag set at all.
To view the new field, select an existing project and scroll to the far right of the details section. It will appear blank.
This can be checked via the User Access dialog.
When creating a brand-new project, the restrict flag will be auto set to no, so this will need to be changed to yes for the changes to be to come into effect.
Once updated all users will not have access to this project until they have been granted access by the Project Manager/Sys Admin.
Finally, the Restrict Project drop down does have its own tooltip to explain what it does.