A mobile telephone is used to diagnose a computer with malware. The telephone becomes a bootable device with a bootable partition in persistent storage. An operating system image including antivirus software in the bootable partition of the telephone is used to bootstrap the affected computer. The antivirus software executes upon the computer and transfers results (files, checksums, registry data) to the mobile telephone. The telephone uploads these results to a remote cloud service which then develops instructions, patterns, files, etc. for counteracting the malware. The cloud service downloads this response to the mobile telephone which then transfers the response back to the computer. The antivirus software on the computer uses the response to remove the malware on the computer. An interface application on the mobile telephone handles transfer with the computer and uploading and downloading with the cloud service.