With ADS in Windows, a stream can be opened for a file like "test.txt:ea.ini", so I can have some data that is visible in "test.txt" and other data that is "hidden" in the ADS "test.txt:ea.ini". I can see the "hidden" data by just opening the file with notepad and specifying "test.txt:ea.ini".
QFile works just fine with ADS, and QSettings was working, but somewhere between Qt 4.8 and 5.4 this functionality was broken. If I create a QSettings object with "tests.txt:ea.ini", I will get an access error now. QFile still works fine.