1. A computer implemented method for securing software modifications in a virtualized computing environment, said method comprising: under the control of one or more computer systems configured with executable instructions, providing at least one application programming interface (API) configured to receive requests submitted to a host computing device, the host computing device including a virtualization layer configured to host one or more guests; storing a public key capable of being used to decrypt information on the host computing device, wherein a corresponding private key capable of being used to encrypt the information is stored in a secure location that is external with respect to the host computing device; receiving, by the host computing device over the API, a request to execute a privileged operation in the virtualization layer of the host computing device, the request signed using the private key stored in the secure location; and executing, by the virtualization layer, the privileged operation if a signature of the request is successfully validated using the public key, wherein the privileged operation fails if the signature of the request is unable to be successfully validated using the public key.