http://y7yea4pmqqtznb33qiugvysyn2bob5v62e4pvoadoibrwkq3tsddjeyd.onion/ps/pages/about-surveillance-self-defense
OPSEC is the process of protecting information about one's activities that may be important to a potential adversary. This is a process that frequently goes beyond the digital realm. For example, people trying to have confidential meetings may have to worry about whether someone physically followed them, whether they were observed by CCTV cameras, whether their neighbors might have become aware of the meeting, or whether their meeting places have been bugged.