Too many people have been spied upon by too many Government agencies and too much information has been illegally collected. The Government has often undertaken the secret surveillance of citizens on the basis of their political beliefs, even when those beliefs posed no threat of violence or illegal acts on behalf of a hostile foreign power. The Government, operating primarily through secret and biased informants, but also using other intrusive techniques such as wiretaps, microphone "bugs", surreptitious mail opening, and break-ins, has swept in vast amounts of information about the personal lives, views, and associations of American citizens. Investigations of groups deemed potentially dangerous—and even of groups suspected of associating with potentially dangerous organizations—have continued for decades, despite the fact that those groups did not engage in unlawful activity.