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BOX Drive installs cbfsconnect2017.sys which disables support for Microsoft's Bypass IO (directstorage)

  • May 23, 2025
  • 4 replies
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BOX drive, including the latest version, installs a legacy minifilter called cbfsconnect2017.sys version 2017.0.24.104.  When this filter is installed, it causes Microsoft's Bypass IO (directstorage) support to be disabled.  BOX Drive will not function without this driver, and I've verified that once BOX Drive is removed along with cbfsconnect2017.sys, Bypass IO functions once again.   Installing BOX Drive once again installs cbfsconnect2017, breaking Bypass IO. 

I did note in my testing that when HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\I/O System\ IoBlockLegacyFsFilters is set to 1 (legacy file filters drivers are blocked from loading or attaching to storage volumes), cbfsconnect2017.sys is not loaded but BOX drive does launch and appear to work. 

This should be entered as a bug and noted.  I believe the company behind cbfs connect (callback technologies) does have a more modern version of their virtual filesystem interface. It's also possible that the app has some legacy code that is still looking for and installing cbfsconnect2017, but it no longer used. 

    4 replies

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    Hi Jeffrey, 

    Welcome to Box Community and glad to assist! 

    A member of our team will step in to provide assistance. Please keep an eye out and we'll send an email. 

    Thanks for posting! 

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    I confirm this issue too. Here are the symptoms:

    Use this command in command prompt: fsutil bypassIo state c:\

    It will state that the drive is not bypassio compatible. And although the minifilter mentioned above is the cause, it shows as blank when identifying the causative minifilter. Other minifilters that have caused this issue (e.g. Malwarebytes, Bitdefender Total Security, EaseUS partition magic, others) have their minifilter identified. But the minifilter used by Box shows up blank.

    For now the only solution is to uninstall Box and restart the PC, which is what I'm doing across all my gaming machines.

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    Instead of removing BOX, if you set this registry entry, it will allow BOX to continue to run and bypassio works too.  I've so far found no downside to this, although BOX needs to get off the retired version of that virtual filesystem driver and move to one that is supported by the vendor:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\I/O System\

    Add:  DWORD:  IoBlockLegacyFsFilters  and set it to 1 (legacy file filters drivers are blocked from loading or attaching to storage volumes), cbfsconnect2017.sys is not loaded but BOX drive does launch and appear to work.

     

    This is what Callback Technologies had to say (maker of the virtual filesystem driver)

    cbfsconnect2017.sys contains two drivers – a filesystem _filter_ driver (which you are blocking) and the main driver which is a filesystem driver (not a filter). I can’t say immediately how the used build of version 2017 works, but IIRC, the main filesystem driver ignores the missing filter part and continues to work. Actually, that filter can be disabled from the code side, but again, I am not sure if this is so in version 2017. The filter is not required for main operations. 

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    Thanks. Good workaround. I opted to not mess with registry files (although it is very easy). Instead I'm using OneDrive. I also used pCloud for a bit. It uses ELDOS CBFS, and their CBFS implementation does not interfere with bypassIO.

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