The most effective security control to mitigate the risk of users granting non-verified software access to corporate data would be option C: "Update the BYOD (Bring Your Own Device) policy".
Here's why:
A. "Block access to application stores" - This could be effective in some cases, but it might not be practical or feasible in many situations, especially if employees use their personal devices for work. It also doesn't prevent the installation of non-verified software from other sources.
B. "Implement OTA (Over The Air) updates" - While it's important to keep devices updated for security reasons, this doesn't directly address the issue of users granting access to non-verified software.
C. "Update the BYOD policy" - This is the most direct and effective way to address the issue. The policy could be updated to include rules about what types of software can be installed on devices that are used for work, and it could provide guidelines for how to verify the security of software. This would educate users about the risks and help prevent them from inadvertently granting access to non-verified software.
D. "Deploy a uniform firmware" - This could help ensure that all devices have the same security features and updates, but it doesn't prevent users from installing non-verified software. It also may not be feasible if employees are using a variety of different devices and operating systems.
Remember, the effectiveness of these controls can vary depending on the specific context and needs of the organization. It's important to consider all factors and possibly implement a combination of controls for optimal security.