Phoning home may be useful for the proprietor in tracking a missing or stolen computer. This type of phoning home is frequently used on mobile computers at corporations. It typically involves a software agent which is difficult to detect or remove. However, there are malicious types of phoning homes such as surreptitious communication between applications or hardware installed at end-user sites and their manufacturers or developers. The traffic may be encrypted to make it difficult or impractical for the end-user to determine what data are being transmitted.