Information
Hot corners _MUST_ be disabled.
The information system conceals, via the session lock, information previously visible on the display with a publicly viewable image. Although hot comers can be used to initiate a session lock or to launch useful applications, they can also be configured to disable an automatic session lock from initiating. Such a configuration introduces the risk that a user might forget to manually lock the screen before stepping away from the computer.
Solution
This is implemented by a Configuration Profile.
mobileconfig profile info:
com.apple.ManagedClient.preferences:
com.apple.dock:
wvous-bl-corner
0
wvous-br-corner
0
wvous-tr-corner
0
wvous-tl-corner
0