If hypervisor compromised, so potentially are 'private cloud' tenants
Amazon offers p-rivate cloud in a multi-tenant setting. The VPN and other connections are private, but on the same multi-tenant server sits a customer with an unsecured desktop. That's OK, provided there's no breach in the barriers imposed by the hypervisor, points out Scalr's Sebastian Stadil. If there is a breach, then Amazon's concept of private cloud as well as customers' "private" production systems are at risk. That's probably part of the reason Amazon is acting with such urgency in this case.