Minimum amount of NTFS permissions granted to user, but still need the ability to perform FLR’s.
In order to perform a file level restore the minimum NTFS permissions you will need for the directory selected is “List Folder Contents”.
Setting the directory permissions to reflect these access rights will allow the FLR to mount, and see the files/folders.
Subsequently this will restrict the backup operator from opening the files/folders, and still allow the FLR to process normally. The FLR service account will require Read/Write access rights to copy the file. The “List folder Contents” is the minimum permission which will allow the GUI operator to enumerate, and list the files in the directory selected. Once the files have been selected the service account (which would in theory be a different account with higher access privileges which can perform the actual file copy operation.