In D2L, students were not able to access the Manage Files tool, but in Canvas students are able to access the analogous tool (Files). If instructors wish to upload files to their Canvas site, and prevent students from accessing the files, there are a few different options to keep in mind.
Upload the file to Files, but then unpublish or restrict the file
Files uploaded to the Files tool are published (i.e. available to students) by default. https://community.canvaslms.com/docs/DOC-2770 contains information on how instructors can restrict both files and folders from students by changing either the published status of the file, or setting date restrictions.
Upload the file to Files, create a link in Modules, but then unpublish the link in Modules
If a file is linked to from Modules, students can see it is there, but aren't able to click on the file to access it. https://community.canvaslms.com/docs/DOC-2822 has information about publishing or unpublishing a module, and a file that is under an unpublished Module can not be accessed by students.
Remove the Files tool from the course navigation
Instructors can remove the Files tool from the course navigation area by following the steps on https://community.canvaslms.com/docs/DOC-2555.