Sensors are everywhere and they have become part of our daily lives. We have sensors in our heating systems, air-conditioning systems, supermarkets, airports, shopping malls, and even in offices. These sensors are continually monitoring the environment, events, activities, people, vehicles, and many other objects, gathering data from these objects, aggregating the data, and then making sense out of the data and finally taking actions based on the analysis of the data. For example, we have sensors to monitor the temperature of a manufacturing plant periodically and if the temperature exceeds a certain value, then raise an alarm. At the other extreme, we now have sensors monitoring the activities of people and if

these activities are considered to be suspicious, the law enforcement officials are notified. We also now have biological sensors that can perhaps detect whether an individual is carrying a biological agent such as anthrax. If so, the sensor then alerts appropriate health and law enforcement officials so that prompt actions can be taken. Sensors are also being employed to detect the spread of smallpox and other diseases. Video surveillance cameras that have embedded sensors can be found on highways to detect speeding and also in shopping malls to detect theft. Finally sensors are being used to detect insider threats both in physical as well as in computing environments. That is, sensors are everywhere.