Invisible GIFs (Tracker GIF, Clear GIF)

A record of all the Web page addresses you have visited during a specific online session. Click trails tell not just what Web site you visited, but also which pages inside that site.
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Web beacons are images that are placed in HTML documents (Web pages, HTML email) to facilitate user activity tracking. Web beacons are usually used in conjunction with cookies and are often used to track visitors across multiple internet domains. Web beacon images are usually, but not always, small and “invisible. ”
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An overlaid image that is invisible to the naked eye, but which can be detected algorithmically. There are two different types of invisible watermarks: fragile and robust.
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A method of steganography that uses a special ink that is colorless and invisible until treated by a chemical, heat, or special light. It is sometimes referred to as sympathetic ink.
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Short name referring to investigation, study, and control of compromising emanations from information system equipment. The study and control of electronic signals produced by various types of electronic hardware, such as computers, televisions, phones, and so on. Its primary goal is to prevent EM and RF radiation from leaving a strictly defined area so as to eliminate the possibility of external radiation monitoring, eavesdropping, and signal sniffing. The study and control of spurious electronic signals emitted from electronic equipment. TEMPEST is a classification of technology designed to minimize the electromagnetic emanations generated by computing devices. TEMPEST technology makes it difficult, if not impossible, to compromise confidentiality by capturing emanated information.
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