A client system, such as a computer or a smartphone, securely exchanges sensitive information with a remote service provider computer system such as a bank or an online retailer. The client system executes a commercially available operating system in an untrusted virtual machine (VM), which may be affected by malware. A hypervisor is configured to launch a trusted, malware-free VM from an authenticated image stored on computer-readable media used by the untrusted VM. The trusted VM executes a thin operating system with minimal functionality, to manage a secure communication channel with the remote server system, wherein sensitive communication is encrypted. Data from the trusted VM is forwarded via the hypervisor to a network interface driver of the untrusted VM for transmission to the remote service provider. The service provider may perform a remote attestation of the client system to determine whether it operates a trusted VM.