US government agencies have been buying, to some degree, details of Americans' internet activities from data brokers

Multiple military intelligence offices have paid a data broker for access to internet traffic logs, which could reveal the online browsing histories of U.S. citizens, Sen. Ron Wyden said in a letter Wednesday, citing an anonymous whistleblower that had contacted his office.

The previously unknown government procurements, revealed in a Wednesday Vice report, have already triggered alarm bells from a prominent U.S. Senator and the American Civil Liberties Union, which told Gizmodo there's still far too little known about how the DoD's making use of the tool which can "reveal extremely sensitive information about who we are and what we're reading online," Wyden wrote. At the very least, the purchase represents the latest example of government agencies potentially finessing their way around constitutional protections by seeking out data from shady data brokers and other private firms.

In America, the Fourth Amendment protects people against unreasonable searches and seizures, which is why law enforcement agencies generally need to obtain a warrant before they can demand data from or about a third party under investigation. Wyden's concern is that government agencies are flouting the Fourth Amendment by obtaining information from third-party data brokers and bypassing the judicial review process required under the law.

Wyden said he has been investigating the government's purchase of location and web browsing records for several years but has been stymied by the Pentagon. The Defense Department last year responded to his queries but applied a classification that prevents Wyden from making the details public. And the Democrat senator's efforts to have that restriction removed have been rebuffed.

"According to the whistleblower, NCIS is purchasing access to data, which includes NetFlow records and some communications content, from Team Cymru, a data broker whose data sales I have previously investigated," Wyden wrote.

Wyden says public records indicate that NCIS has a contract to use Augury, a subscription service offered by Team Cymru that "provides access to email data ('IMAP/POP/SMTP [packet capture] data') and data about web browser activity ('cookie usage,' 'UserAgent data', and 'URL accessed')."