A host computer system may be configured to connect to a network. The host computer system may be configured to implement a workspace and an isolated computing environment. The host computer system may be configured to isolate the isolated computing environment from the workspace using an internal isolation firewall. The internal isolation firewall may be configured to prevent data from being communicated between the isolated computing environment and the workspace, for example, without an explicit user input. The host computer system may be configured to implement one or more mechanisms that prevent malware received by the host computer system from receiving external communications from an external source. The one or more mechanisms may be configured to prevent control of the malware by the external source. The one or more mechanisms may be configured to prevent the malware from establishing a command channel with the external source.