Let's say I have VirtualBox or Vmware Workstation on a Windows 10 Pro host, hosting Windows or a Linux distribution such as Ubuntu or CentoS). If I have an antivirus or Internet Security software on the Windows host, could it protect Windows or Linux VM's? Can any consumer, SOHO, or small business version of Norton, Avast, BitDefender, Kaspersky, McAfee, or other security software, protect virtual machines while the security software is on the host operating system?
The answer is bit of yes and no, but in some cases, it is a definite no. It really depends on what security software you are using, and what type of virtualization software you are using.
A traditional antivirus program that just scans a host computer cannot protect your VM. The reason being as @schroeder said, "An AV on the host cannot access the memory or filesystem in a VM."
If you are using an internet security software that has a HIPS (Host Intrusion Prevention System) feature that acts like a network firewall, the answer is bit of yes and no. The yes part is if the VM program tries to send a request (considering that you are using a browser inside a VM, like VirtualBox), thru the host to access a website. In the scenario that the HIPS detects the destination of the request or source address of the data received listed in a global or local blacklist, the HIPS would drop the data. In that case, the VM would not receive anything. The no part is related to the fact that the security software would not be able to access the memory or the filesystem of the VM to scan for viruses.