Apple added a new security feature in High Sierra 10.13.2 whereby KEXT drivers had to be approved by the user. Software like virtualisation software i.e. VirtualBox and Anti-Virus software are the most common cases for users to encounter this.
In an enterprise environment it is possible to 'pre-approve' these KEXTs on behalf of a user using an MDM - Mobile Device Management solution. Home users will of course not be using an MDM and would need to manually approve them.
Normally this is done in System Preferences -> Security & Privacy. The following article although for a different KEXT shows how this would be done.
https://helpdesk.egnyte.com/hc/en-us/articles/115002904012-How-to-Approve-Egnyte-s-Kernel-Extension-in-macOS-High-Sierra-and-Mojave
Sadly I have seen VirtualBox still get stuck. It seems the programmers of VirtualBox are not very good at writing Mac software.
So the instructions given by av2222 sound like a way to get round that.
However in answer to your question - how did he find that string? When you install a piece of software which installs a KEXT this is added to a list managed by Apple's security software. This list contains the ID number assigned to the developer of that software. It is possible to view this information and display a list of these values.
See - https://technology.siprep.org/getting-the-team-id-of-kernel-extensions-in-macos-10-13-and-higher/
However a much more thorough check for these KEXT strings is achieved using the script provided on the following web page, I used this script and got a list of about 20 different ones on my Mac.
https://www.richard-purves.com/2017/11/09/mdm-and-the-kextpocalypse-2/
Note: Some KEXTs are installed by Apple as standard. Somewhat illogically even though Apple have provided and installed these as standard they are still not automatically trusted. This particularly applies to drivers for various PCIe SATA and SATA RAID controllers from HighPoint, Atto, SoftRaid, CalDigit etc.
