some encryption strategies sanitize the disk by filling it with random data, which not only is incompressible, but may trigger disk growth.This may or may not have undesirable consequences (e.g. the virtual machine's FS is now encrypted, which makes it incompressible.By knowing this password, it is possible to mount the VM as an external volume, thereby accessing the data. the VM now requires someone knowing the master password at boot (think downtime).file sharing so you will want to have it disabled or uninstalled, and the various communication channels properly secured. it will be possible, if difficult (through #1) to force entry through e.g.Systems that are invulnerable to CBA are being studied, but these results will likely not affect VMs, where a suspended machine state attack will still be possible. it will still be possible (not easy) to access the virtual machine's 'virtual RAM', and in some cases also modify it, in a version of the 'cold boot attack'.You encrypt the whole partition so that a master password is needed at boot.

What is virtualbox encryption