Another way to control this setting is by using an undocumented registry key AutoDetect=0 mentioned on this blog post:
Registry Key :
HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings\
DWORD
AutoDetect
= 0 or 1
So the .reg file to turn it off would look like:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"AutoDetect"=dword:00000000