Not all virtualization technology is equal in the security department. This is true for multiple different reasons. First of all I hear from good hackers that full hardware virtualization systems like VMware and Virtual Box are harder to break out of than OS virtualization solutions like freebsd jails. Of course, you can layer multiple types of virtualization. Second of all, between the full hardware virtualization solutions there are differences in security based on the correctness of the hypervisor. I have heard that VMware and Virtualbox are so complex that their hypervisors are pretty much ensured to be penetrated by any talented hacker, they probably have plenty of 'jail breaking' flaws waiting to be discovered and exploited. However, this does require a talented attacker and even if there is a talented attacker using virtualization like this can buy you time (in which to detect them with intrusion detection software) and cost the attacker more resources (they still need to find an additional vulnerability to break out of the hypervisor). Of all the solutions for virtualization I have heard the best things about Xen as far as security is concerned, Qubes is an OS based on the xen hypervisor but I think they use an even leaner version to try to lower complexity and increase correctness (more complexity equals less correctness, as a general rule of thumb). I doubt many law enforcement level attackers can break out of Virtual Box or even VMware hypervisor, even the ones talented enough to do basic hacking attacks against servers / sites and such.