[…] New Bitlocker features in Windows 10, version 1507:
* DMA port protection. You can use the DataProtection/AllowDirectMemoryAccess MDM policy to block DMA ports when the device is starting up. Also, when a device is locked, all unused DMA ports are turned off, but any devices that are already plugged into a DMA port will continue to work. When the device is unlocked, all DMA ports are turned back on.
This policy setting allows you to block direct memory access (DMA) for all hot pluggable PCI downstream ports until a user logs into Windows. Once a user logs in, Windows will enumerate the PCI devices connected to the host plug PCI ports. Every time the user locks the machine, DMA will be blocked on hot plug PCI ports with no children devices until the user logs in again. Devices which were already enumerated when the machine was unlocked will continue to function until unplugged. This policy setting is only enforced when BitLocker or device encryption is enabled.