Mobile device confiscated by CBP

Does anyone have any insight into what actually transpires when US Customs and Border Patrol confiscates a mobile device from a traveller. The CPB had the device for close to 40 minutes and hooked it up to a device. I assume an image was taken, but what I'm curious about is if anything was installed.

A review of the device, once returned, shows no evidence of anything being installed.

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