Surveillance Self-Defense

[ssd.eff.org] The Electronic Frontier Foundation (EFF) has created this Surveillance
Self-Defense site to educate the American public about the law and
technology of government surveillance in the United States, providing
the information and tools necessary to evaluate the threat of
surveillance and take appropriate steps to defend against it.

Surveillance Self-Defense (SSD) exists to answer two main questions:
What can the government legally do to spy on your computer data and
communications? And what can you legally do to protect yourself against
such spying?

Source: https://ssd.eff.org