Comment # 30 on bug 1174406 from Larry Finger

The files belonging to root:vboxusers should be as follows:

In /usr/lib/virtualbox/
* VBoxNetNAT
* VBoxNetDHCP
* VBoxNetAdpCtl
* VBoxHeadless
  VBoxPermissionMessage
  VBoxSUIDMessage
  VBoxUSB_DevRules
  VirtualBox6
* VirtualBoxVM
* VBoxSDL

Files marked with an * are SUID.

In /etc/
vbox/
vbox/vbox.cfg
vbox/autostart.cfg

The files under /etc are only used for autostart of VMs.

On the web, the only reason listed for USB passthru failing is the user not
belonging to vboxusers. Actually, the GUI will not start if that is the case.

The permissions are set by the permissions package. Running
sudo chkstat --system --set
will ensure that they are set properly.