As mentioned above, Delivery Optimization Files are Windows update files that are stored on your computer and distributed to other Windows PCs. Microsoft ensures that there is no way your PC can be compromised by bad actors during this process. However, if the idea of a stranger grabbing files off your PC gives you the creeps, you can opt out of this program.
To do so, navigate to "Settings -> Windows update -> Advanced options -> Delivery Optimization" on Windows 11, and "Settings -> Updates & Security -> Delivery Optimization" on Windows 10. On this screen, flick the toggle switch labeled "Allow downloads from other PCs" to the off position to opt out. In addition, you'll no longer have Delivery Optimization Files hogging space on your storage drive!