Editor's Note:This is the second in a series of analyses on surveillance and countersurveillance. As far back as the 5th century B.C., Chinese warrior-philosopher Sun Tzu went on record citing the paramount importance of using spies and clandestine reconnaissance to uncover enemy plans. At the time — and for centuries afterward — surveillance involved placing an operative close enough to a target to track his movements or overhear his conversations. Technological advances — especially those that have come along over the past century — have made it possible not only to watch and listen to others from afar, but to do so with ease. Today, technical surveillance is conducted for a wide variety of purposes by individuals as diverse as terrorists, private investigators, activists, paparazzi, peeping toms, law enforcement and governments — and even by parents who listen in on their infants via baby monitors. These people are tracking a subject's activities, usually from a distance or remotely, using devices specifically designed or adapted for that purpose such as global positioning system (GPS) locaters, sophisticated listening devices and cameras of all kinds. Al Qaeda used technical surveillance when targeting financial institutions in Washington, D.C., New York and Newark, N.J., and potential targets in Singapore in 2003. In New York, for example, several operatives sat in a Starbucks café across the street from their intended target and recorded various aspects of the institution's security measures and building access. Their notes and some of their videos were found on a laptop computer after authorities broke up the cell. Although al Qaeda's uses less-sophisticated technology than some — hand-held cameras versus micro-cameras and bionic ears, for example — the network's ability to conduct technical surveillance still is formidable. Environmental activists, animal rights activists, anarchists and anti-globalization activists frequently surveil their subjects before staging a protest or "direct action" operations. Groups that target corporations for sabotage, such as the Earth Liberation Front, are especially sophisticated in the use of technical surveillance. The Ruckus Society is a group devoted to training activists in "electronic scouting" — technical surveillance involving the use of remote cameras, GPS locators, frequency counters, programmable scanners and night-vision goggles. Program graduates, then, utilize high-tech equipment such as miniature remote cameras and "bionic ear" listening devices to conduct their surveillance. These activists frequently use programmable scanners and cameras to monitor security/police communications and activity in order to warn the saboteurs of an impeding response by law enforcement. In some countries, it is not uncommon for Western business or government travelers to find telltale signs of listening devices in their hotel rooms, offices, meeting rooms and chauffeur-driven cars. In other instances, people have been caught spying on others in public bathrooms and changing rooms using tiny cameras that can be concealed in something as seemingly innocuous as an air freshener or electrical outlet. The accessibility and miniature size of today's surveillance equipment makes it easy for just about anyone to clandestinely watch another. As technology continues to advance and surveillance becomes even more ubiquitous, methods to thwart such eavesdropping also will improve.