"Magic Lantern"

I came across this item while watching a re-run of the Law and Order TV program; this one dealing with a computer company that was selling information about a person's private life to anyone who asked for it.  It so happened that the one asking was a stalker and the person who's private life was divulged wound up dead.  The program noted that the federal government had a similar program-called "Magic Lantern"-that allowed the federal government to gain access to a person's email account and know what they were thinking and saying even as they were saying it.  This program came about under the US Patriot Act passed after 9/11.  What happens is that the government can plant a computer virus on a computer and then read everything being recorded there; even what I am now writing.  I believe a warrant is needed but it might come from a FISA court not an open criminal court.  There is some comment here about a "Enhanced Carnivore Project" that is meant to detect terrorist suspects.  The ACLU and others have fought this authority but to no avail (as I understand it).  An internet site-"Cotse.Net" stated that the program "...was useless against suspects clever enough to encrypt their files".  I admit, my knowledge of computers and this program are limited but the overall idea sounded really dangerous to me.