A group of U.S. senators from both sides of the aisle sent a strongly worded letter to tech companies and advertisers. The letter describes a process called real-time bidding and questions the gathering of bitstream data The senators say this data can easily fall into the hand of other countries, looking to gather information. The companies that received the letter have to answer to several requests by May 4: Please identify the specific data elements about users, their devices, the websites they are accessing, and apps they are using that you provide to auction participants.”]