The questions ranged from where the companies cull their data about consumers to what method the companies use to procure this information. He also asks the companies to list third parties they share the data with and what type of information is provided to these entities.
"Because your industry has monetized consumer data, it is critical that we understand what information companies like yours are already collecting and selling," Rockefeller wrote. "Yet, answers to basic questions remain elusive."
Rockefeller notes that the industry has attracted scrutiny in recent years from the Federal Trade Commission (FTC), which has argued that data broker companies' efforts to establish consumer privacy rules have fallen short. The Senate Commerce chairman sent letters to Acxiom, Experian, Rapleaf, Datalogix, Epsilon and Spokeo, among others.
Privacy groups have recently called on the FTC to investigate whether Facebook's partnership with data-mining company Datalogix violates the terms of a settlement the trade agency finalized with the social networking company.