Running Windows XP in a corporate setting here. I have an issue where a filter driver is interfering with the functionality of different USB HIDs. For example graphics tablets do not respond while the filter driver is in place. I've also had the issue with foot pedals used with transcription software.

My question is really two fold:

A) what makes Windows use a filter driver on one HID but not another?

B) when a filter driver is causing conflicts how can I disable it on the affected devices?


I've previously narrowed down the issue to the filter driver by uninstalling the software (Funk Proxy Host) responsible for the filter driver. The software is a type of RDP we use here at work. (I might have even booted into safe mode and renamed the file, I forget).

I believe the filter driver is present to disable or modify the use of the local keyboard and mouse while admin staff are assisting users. Either way I don't have the authority to just go uninstalling this software.

As far as I can tell the software versions are the same, however I'm not sure if the device driver definitions are all the same as I don't know where these things would be located.

To check for the presence of the filter driver I locate the hardware device in Device Manager, click Properties > Driver tab > Driver Details.... It shows up as ph32ihid.sys.

Even though all machines are meant to have the same SOE and do have Funk Proxy Host installed I don't always have issues with the same HIDs. A few machines here the foot pedals without any issues. I've not had any machines work with the graphics tablet without uninstalling Funk software.

Driver details

I've just read up a bit more about filter drivers and found the drivers description in the registry under "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ProxyHostHIDFilter" There it's called "Kernel-mode HID filter driver for the Proxy Host". Presumably I could also disable it here but that would be system wide which is probably not desirable?


You can in fact disable it from


by changing the value of the Start entry to 0x4. Source: Microsoft Support

  • Awesome work! Tested this and it works great. – snoopen Dec 4 '12 at 21:34

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