DHS is using its "Automated Targeting System" to spy on Americans.

The Department of Homeland Security (DHS) has proposed to exempt its "Automated Targeting System" from certain Privacy Act provisions. The Automated Targeting System creates "risk-based" profiles of individuals traveling to, from, and throughout the United States. The profile contains a plethora of personal data, including, nationality, race, occupation, and biometrics. The System accesses and "ingests" this information from many sources, including government databases and commercial data aggregators.
http://www.gpo.gov/fdsys/pkg/FR-2012-05-23/pdf/2012-12395.pdf

DHS has issued a final rule exempting its Operations System from various Privacy Act safeguards, including provisions that permit individuals to access information about them held by the agency. The system "fuses" information from many sources which the agency uses for investigatory purposes. There are over twenty categories of data, including social security numbers, citizenship, medical records, and even information gathered from social media in the database.
http://www.gpo.gov/fdsys/pkg/FR-2012-06-07/pdf/2012-13778.pdf