Over a century ago, President Roosevelt brought antitrust enforcement into the heart of American democracy by declaring war on the steel, rail and oil trusts. His concern was driven, as antitrust scholar Tim Wu argues in “The Curse of Bigness,” not only by their threats to the free market, but by the recognition that the power of these leviathans represented an existential threat to democracy.

But imagine how Roosevelt would react to Big Tech — led by Google, Facebook, Apple and Amazon. Because while these companies represent similarly unchecked power, they are different and more dangerous in character than the oil and steel malfeasants of past ages.

The monopolists of a century ago monopolized production by subduing or absorbing competitors. But most of the Big Tech giants haven’t just monopolized a specific product or service; instead, they are networks that have monopolized our interactions with each other and used them as a base for dominating the economy.

Big Tech collects and manages an unthinkably large amount of information about who you are and what you do. And once they have this incredible asset — the story of your life, gleaned from your daily activities — it becomes easy for them to enter and conquer new markets, for they already know as much or more about those markets’ customers than the incumbents they challenge.

Take Amazon, as an example. After enticing consumers with their vast retail buffet, they now use the data they’ve collected to enter the marketplace themselves and undercut competitors who rely on their platform to reach customers. Apple seems to now be following the same playbook, using its iron control over the iOS apps market to demand a 30% kickback on in-app purchases and subscriptions, and then shutting out competitor apps once it steals their best ideas. It’s a strategy that hearkens back to Rockefeller threatening higher railroad prices to arm-twist smaller refineries to succumb to his monopoly.

Google, meanwhile, has monopolized its role as intermediary between you and the world’s information. While demanding “neutrality” for others in the internet space, Google’s exploitation of its massive trove of your personal search, email and location data has been anything but. As competitors such as Yelp and others have shown, Google routinely drives consumers to its own products or to high-paying advertisers, even when other search results are actually more relevant. Its YouTube arm does the same for entertainment, undercutting the royalties due to the creators of film, television and music, often forcing them to compete with their own, pirated content.

Facebook is no different. It has been caught repeatedly lying about how it shares our private data and, like Google, it scrapes the content from newspapers, television and films while hiding behind “safe harbor” laws that shield it from effective prosecution and discipline. And that’s before we consider the filth that thrives on its network — child sexual abuse images, disinformation aimed at undermining our democracy, terrorist propaganda.

Practices such as these have made the Big Tech companies Goliaths. Google, Amazon, Facebook and Apple collectively have a market capitalization of $3 trillion — 10% of the entire American stock market. Researchers have found Google tracks your online movements on 80% of the world’s websites. Together, Google and Facebook claim 70% of all online advertising revenues.

But the world is beginning to notice. In May, the Supreme Court gave a green light for an antitrust suit to proceed against Apple. In September, Google was fined $170 million by the FTC and New York Attorney General for illegally tracking underage kids online. Just days later, the Attorneys General from 50 states and U.S. territories announced a joint antitrust investigation of the search giant — an overdue display of bipartisan cooperation in this hyperpartisan era. And Facebook too faces antitrust and criminal investigations at the state and federal levels.

But Google’s plans have not been slowed. Even in the face of multiple antitrust investigations, it is moving ahead with a plan to take over much of the internet’s Domain Name System — the internet’s “phone book,” which has historically been a decentralized, redundant, consensus-driven system. Shamelessly citing privacy concerns, Google plans to start re-routing all DNS requests coming from Chrome browsers or Android mobile devices through its own proprietary system — an unprecedented centralization of the internet’s core directory in the hands of a single monopolist.

A century ago, Roosevelt recognized that a new threat required a new response. Today, we again see a new and perhaps more serious threat, not just to the promise of the internet, but the future of our economy and democracy. We need to formulate a thoughtful plan to break up these monopolies so that consumers are protected from predatory practices, while still receiving the services they were promised.

Who will be our era’s Teddy Roosevelt?

Ev Ehrlich (Twitter: @evehrlich) served as undersecretary of commerce for President Bill Clinton. He is president of ESC Company, an economics consulting firm.