Leslie Cauley of the USA Today found the "National Security Agency had been secretly collecting the phone call records of tens of millions of Americans, using data provided by AT&T, Verizon and BellSouth." Cauley's sources say the agency uses the call data to "analyze calling patterns in an effort to detect terrorist activity" but that it does not listen in on phone calls. The three carriers are the nation's largest telecommunications companies, providing local, long-distance and wireless phone service, and Internet access. "Only Qwest has refused to help the NSA, the sources said. According to multiple sources, Qwest declined to participate because it was uneasy about the legal implications of handing over customer information to the government without warrants."