Some Linux distributions, for example Debian, do not provide tools that VirtualBox uses to verify kernel module signatures. If VirtualBox can't verify a module's signature, it will attempt to rebuild the kernel module on system boot. This can cause boot delays and the need to re-sign modules every time the machine is rebooted.
On the host machine, edit the file
This tells VirtualBox not to check signatures on boot, but to load the modules and leave it to the kernel to check module signatures.
If you set the variable to any value other than 1, it has no effect.