Although the word surveillance in French literally means "watching over", the term is often used for all forms of observation or monitoring, not just visual observation. Nevertheless, the all-seeing "eye in the sky" is still a general icon of surveillance. Surveillance in many modern cities and buildings often uses closed-circuit television cameras. Although surveillance can be a useful tool for law enforcement and security companies, many people have concerns about the loss of privacy.

The word surveillance is commonly used to describe observation from a distance by means of electronic equipment or other technological means. For example:

• eavesdropping
• telephone tapping
• directional microphones
• covert listening devices or "bugs"
• Minox subminiature cameras
• closed-circuit television
• Night vision
• GPS tracking
• Multilateration
• Bait car
• electronic tagging
• CCTV Images
• Air Traffic Control (ATC) Radars
• military reconnaissance
• Reconnaissance aircraft, e.g. Lockheed U-2
• Reconnaissance satellites
• "trusted" computing devices
• Internet and computer surveillance

However, surveillance also includes simple, relatively no- or low-technology methods such as direct observation, observation with binoculars, postal interception, or similar methods.

Impact of surveillance

The greatest impact of computer-enabled surveillance is the large number of organizations involved in surveillance operations:

• The state and security services still have the most powerful surveillance systems, because they are enabled under the law. But today levels of state surveillance have increased, and using computers they are now able to draw together many different information sources to produce profiles of persons or groups in society.
• Many large corporations now use various form of "passive" surveillance. This is primarily a means of monitoring the activities of staff and for controlling public relations. But some large corporations actively use various forms of surveillance to monitor the activities of activists and campaign groups who may impact their operations.
• Many companies trade in information lawfully, buying and selling it from other companies or local government agencies who collect it. This data is usually bought by companies who wish to use it for marketing or advertising purposes.
• Personal information is obtained by many small groups and individuals. Some of this is for harmless purposes, but increasingly sensitive personal information is being obtained for criminal purposes, such as credit card and other types of fraud.