SkieWhen should I block SD cards and external storage on managed tablets?
Block SD cards and external storage when you do not want files moving in or out on removable media. It is an optional Skie protection using Android's physical media restriction, and it is off by default. It suits exam rooms, shared labs and any device where data should stay on the tablet.
Some tablets and phones take a microsd card or an OTG drive. Files can arrive on one and leave on another: a leaked paper, a video, a pirated game, an app package. A card also gives a way to carry data from one device to the next without touching the network.
Skie sets DISALLOW_MOUNT_PHYSICAL_MEDIA as the device owner. Android then refuses to mount external media, so a card or drive that is plugged in is not read. The restriction applies to media the device might otherwise mount, and the tablet's own storage is unaffected.
It is optional because the default is meant to suit the widest range of schools. Some classes work with files on a card, for instance a media class sharing video projects. Some tablets have no slot at all, in which case the switch simply has nothing to do.
Look at it next to USB data and USB file transfer, which have their own entries. File transfer is blocked by default, and USB data can be disabled entirely where the hardware allows. This card switch handles the removable-media route those do not cover.
The admin sees one toggle in the hardening section, with its state read back from Android and included in the compliance score. Practical tip: turn it on for exam groups and for any set of tablets that has a card slot you are not using. Leave it off where a teacher has a clear reason to use cards.