Once CALEA was in place, requiring systems and equipment that allowed for easy surveillance and interception, the set up was ready for the Patriot Act. On September 11, 2001, tragedy struck in the United States. Two commercial airplanes crashed into the World Trade Center towers. Another was partially retaken by the passengers and crashed in a field, and a fourth crashed into the Pentagon. What unfolded afterwards changed our privacy rights forever. Regardless of how one feels about 9/11, it's important to understand how privacy rights changed - especially how our Internet privacy changed.
Prior to the Patriot Act, one could reasonably assume that email was private. While this too was a largely unfounded notion (forwarding being one reason we cannot consider email to be private), this assumption changed. The federal government made the case that greater protections were necessary to ensure the safety of all citizens. This created quite a stir.
Now, in order to perform surveillance operations on a citizen traversing the World Wide Web, all the government needed to do to start monitoring and intercepting an individual's email was show reason to believe that the person might be a suspected terrorist. In addition to watching U.S. Citizens, the government now had the right to monitor such communications by international citizens. This means that at any point in time, anyone residing in the world who the U.S. government has deemed to be a potential threat may have his or her email being monitored.
Also prior to the Patriot Act, there were some methods for protecting computers so that information could not be accessed. The act gives government officials the right to bypass any firewalls or passwords in order to obtain, monitor and intercept information. Subpoenas can be granted asking for such information and warrants can be granted from any judge - not just those who previously had the authority to grant such surveillance rights.