Governments, enterprises, and consumers face myriad technically advanced and persistent computer threats. Commonly available cyberdefenses such as firewalls, antivirus software, and automatic updates for security patches help reduce the risk from threats. However, they're inadequate because many consumers sometimes ignore the guidance provided or engage in other unsafe actions (such as downloading executable programs from unknown sources). Those with infected computers aren't simply risking their own valuable information and data; they're putting others at risk. One way to address these issues is to use a model similar to the one society uses to address human illness.