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Alternative ways to load a class filter driver

Benjamin_HöglingerBenjamin_Höglinger Member - All Emails Posts: 16

Greetings everyone!

I've come across at least one driver in the wild that somehow manages to act as a class filter driver without having any of the common registry values UpperFilters and LowerFilters in place and without modifying any of the existing device's INF files.

How is this wizardry achieved? Is this a valid practice but simply not publicly documented or most probably some "API-hookery" that runs under the radar of PatchGuard etc.?

And most importantly: how can I do that myself? :grin:

Thanks for reading, cheers

Comments

  • Doron_HolanDoron_Holan Member - All Emails Posts: 10,706
    What class are you seeing this with? And why do you want to go with a potentially undocumented or unsupported way to install a class filter?
    d
  • Benjamin_HöglingerBenjamin_Höglinger Member - All Emails Posts: 16

    Hi Doron,

    as per my emoji this was more of the lighthearted joking side. I am primarily interested in how that is achieved.

    Classes I've seen this with: HICClass, XnaComposite and XboxComposite

    Cheers

  • Benjamin_HöglingerBenjamin_Höglinger Member - All Emails Posts: 16

    A bit more context: I've observed older versions of said driver and back then the authors used the usual way of going with the registry values. For whatever reason (to remain undetected? To work around non-disclosed bugs with another 3rd party driver?) they switched to this "other method" without losing functionality but not being visible in the usual locations (not in Device Manager's filter properties but definitely present in the device's driver stack).

    What got me curious: I found another 3rd party HID device that struggles to boot when a filter is present (bug? intentional? I don't know) and interestingly enough it works with the mysterious class filter nonetheless.

    All very weird jet very interesting.

    Cheers

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