While the user may choose the device to fit their personal requirements, they may purchase and even own it, but they may not expect to have to maintain the configuration and security management requirements. Some users may want or need local admin rights to customize the device to their requirements, while others may expect their IT support to be able to remotely manage and configure the device on their behalf. Understanding and agreeing to who is responsible for the management of the device is key to ensuring that the appropriate level of security is applied.
These considerations then define the appropriate level of trust for each device. For example, if the user has local administrative rights to the device, then they have the ability to modify the configuration, install software, and generally increase the risk profile. A user logging into this device would therefore have a lower level of trust than a device that is enrolled and managed by company policies, and has the user's local admin rights removed.