Booting Installed Windows from VirtualBox in Ubuntu

The host has complete control over the guest. So if there is malware running on the host, the guest is compromised as well.

In practice, most malware out there only tries to infect common software, such as the OS itself, web browsers, media players, etc. Virtual machines are such a rare case that malware authors typically don't bother, especially given that the diversity of systems that could be running inside the VM means a lot of work for the malware author.

However, this may change as virtual machines become more common. For example copy-paste would make a relatively simple infection vector (you think you're copying some innocent text into the VM but the malware makes you in fact paste a command that opens the gates; also, consider that by spying the host clipboard, the malware has access to anything you copy-paste even from within the VM to within the VM). And if you're the victim of a targeted attack rather than some common malware, all bets are off.

If you have a network link between the host and the guest, the malware may attempt propagate that way, like it would to any other machine in your local network.

There are 2 ways, which I normally use

Option 1: Before booting up Ubuntu, inside Virtualbox Ubuntu VM settings, specify a share folder. Then after logged in to Ubuntu, create a new directory for example /media/vboxshared and mount that drive using the command sudo mount -t vboxsf SHARENAME /media/vboxshared. Enter your password when it prompts for the password.

Option 2: Before booting up Ubuntu, add a new Network adapter and select 'Bridged Adapter'. Then after logged in to Ubuntu, run the command ifconfig -a | more to get the ip address of that new network adapter. In Windows, use WinSCP or FileZilla to transfer the file to Ubuntu