EFF has long warned about the dangers of the “real-time bidding” (RTB) system powering nearly every ad you see online. A proposed class-action settlement with Google over their RTB system is a step in the right direction towards giving people more control over their data. Truly curbing the harms of RTB, however, will require stronger legislative protections.

What Is Real-Time Bidding?

RTB is the process by which most websites and apps auction off their ad space. Unfortunately, the milliseconds-long auctions that determine which ads you see also expose your personal information to thousands of companies a day. At a high-level, here’s how RTB works:

1. The moment you visit a website or app with ad space, it asks an ad tech company to determine which ads to display for you. This involves sending information about you and the content you’re viewing to the ad tech company.
2. This ad tech company packages all the information they can gather about you into a “bid request” and broadcasts it to thousands of potential advertisers. 
3. The bid request may contain information like your unique advertising ID, your GPS coordinates, IP address, device details, inferred interests, demographic information, and the app or website you’re visiting. The information in bid requests is called “bidstream data” and typically includes identifiers that can be linked to real people. 
4. Advertisers use the personal information in each bid request, along with data profiles they’ve built about you over time, to decide whether to bid on the ad space. 
5. The highest bidder gets to display an ad for you, but advertisers (and the adtech companies they use to buy ads) can collect your bidstream data regardless of whether or not they bid on the ad space.   

Why Is Real-Time Bidding Harmful?

A key vulnerability of real-time bidding is that while only one advertiser wins the auction, all participants receive data about the person who would see their ad. As a result, anyone posing as an ad buyer can access a stream of sensitive data about billions of individuals a day. Data brokers have taken advantage of this vulnerability to harvest data at a staggering scale. Since bid requests contain individual identifiers, they can be tied together to create detailed profiles of people’s behavior over time.

Data brokers have sold bidstream data for a range of invasive purposes, including tracking union organizers and political protesters, outing gay priests, and conducting warrantless government surveillance. Several federal agencies, including ICE, CBP and the FBI, have purchased location data from a data broker whose sources likely include RTB. ICE recently requested information on “Ad Tech” tools it could use in investigations, further demonstrating RTB’s potential to facilitate surveillance. RTB also poses national security risks, as researchers have warned that it could allow foreign states to obtain compromising personal data about American defense personnel and political leaders.

The privacy harms of RTB are not just a matter of misuse by individual data brokers. RTB auctions broadcast torrents of personal data to thousands of companies, hundreds of times per day, with no oversight of how this information is ultimately used. Once your information is broadcast through RTB, it’s almost impossible to know who receives it or control how it’s used. 

Proposed Settlement with Google Is a Step in the Right Direction

As the dominant player in the online advertising industry, Google facilitates the majority of RTB auctions. Google has faced several class-action lawsuits for sharing users’ personal information with thousands of advertisers through RTB auctions without proper notice and consent. A recently proposed settlement to these lawsuits aims to give people more knowledge and control over how their information is shared in RTB auctions.

Under the proposed settlement, Google must create a new privacy setting (the “RTB Control”) that allows people to limit the data shared about them in RTB auctions. When the RTB Control is enabled, bid requests will not include identifying information like pseudonymous IDs (including mobile advertising IDs), IP addresses, and user agent details. The RTB Control should also prevent cookie matching, a method companies use to link their data profiles about a person to a corresponding bid request. Removing identifying information from bid requests makes it harder for data brokers and advertisers to create consumer profiles based on bidstream data. If the proposed settlement is approved, Google will have to inform all users about the new RTB Control via email. 

While this settlement would be a step in the right direction, it would still require users to actively opt out of their identifying information being shared through RTB. Those who do not change their default settings—research shows this is most people—will remain vulnerable to RTB’s massive daily data breach. Google broadcasting your personal data to thousands of companies each time you see an ad is an unacceptable and dangerous default. 

The impact of RTB Control is further limited by technical constraints on who can enable it. RTB Control will only work for devices and browsers where Google can verify users are signed in to their Google account, or for signed-out users on browsers that allow third-party cookies. People who don't sign in to a Google account or don't enable privacy-invasive third-party cookies cannot benefit from this protection. These limitations could easily be avoided by making RTB Control the default for everyone. If the settlement is approved, regulators and lawmakers should push Google to enable RTB Control by default.

The Real Solution: Ban Online Behavioral Advertising

Limiting the data exposed through RTB is important, but we also need legislative change to protect people from the online surveillance enabled and incentivized by targeted advertising. The lack of strong, comprehensive privacy law in the U.S. makes it difficult for individuals to know and control how companies use their personal information. Strong privacy legislation can make privacy the default, not something that individuals must fight for through hidden settings or additional privacy tools. EFF advocates for data privacy legislation with teeth and a ban on ad targeting based on online behavioral profiles, as it creates a financial incentive for companies to track our every move. Until then, you can limit the harms of RTB by using EFF’s Privacy Badger to block ads that track you, disabling your mobile advertising ID (see instructions for iPhone/Android), and keeping an eye out for Google’s RTB Control.

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Lawmakers in Washington are once again focusing on kids, screens, and mental health. But according to Congress, Big Tech is somehow both the problem and the solution. We're diving into the latest attempt to control how kids access the internet and more with our latest EFFector newsletter.

Since 1990, EFFector has been your guide to understanding the intersection of technology, civil liberties, and the law. This latest issue tracks what to do when you hit an age gate online, explains why rent-only copyright culture makes us all worse off, and covers the dangers of law enforcement purchasing straight-up military drones.

Prefer to listen in? In our audio companion, EFF Senior Policy Analyst Joe Mullin explains what lawmakers should do if they really want to help families. Find the conversation on YouTube or the Internet Archive.

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EFFECTOR 38.2 - ✍️ THE BILL TO HAND PARENTING TO BIG TECH

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Keeril Makan has been appointed vice provost for the arts at MIT, effective Feb. 1. In this role, Makan, who is the Michael (1949) and Sonja Koerner Music Composition Professor at MIT, will provide leadership and strategic direction for the arts across the Institute.

Provost Anantha Chandrakasan announced Makan’s appointment in an email to the MIT community today.

“Keeril’s record of accomplishment both as an artist and an administrative leader makes him exceedingly qualified to take on this important role,” Chandrakasan wrote, noting that Makan “has repeatedly taken on new leadership assignments with skill and enthusiasm.”

Makan’s appointment follows the publication last September of the final report of the Future of the Arts at MIT Committee. At MIT, the report noted, “the arts thrive as a constellation of recognized disciplines while penetrating and illuminating countless aspects of the Institute’s scientific and technological enterprise.” Makan will build on this foundation as MIT continues to strengthen the role of the arts in research, education, and community life.

As vice provost for the arts, Makan will provide Institute-wide leadership and strategic direction for the arts, working in close partnership with academic leaders, arts units, and administrative colleagues across MIT, including the Office of the Arts; the MIT Center for Art, Science and Technology; the MIT Museum; the List Visual Arts Center; and the Council for the Arts at MIT. His role will focus on strengthening connections between artistic practice, research, education, and community life, and on supporting public engagement and interdisciplinary collaboration.

“At MIT, the arts are a vital way of thinking, making, and convening,” Makan says. “As vice provost, my priority is to support and strengthen the extraordinary artistic work already happening across the Institute, while listening carefully to faculty, students, and staff as we shape what comes next. I’m excited to build on MIT’s distinctive, only-at-MIT approach to the arts and to help ensure that artistic practice remains central to MIT’s intellectual and community life.”

Makan says he will begin his new role with a period of listening and learning across MIT’s arts ecosystem, informed by the Future of the Arts at MIT report. His initial focus will be on understanding how artistic practice intersects with research, education, and community life, and on identifying opportunities to strengthen connections, visibility, and coordination across MIT’s many arts activities.

Over time, Makan says he will work with the arts community to advance MIT’s long-standing commitment to artistic excellence and experimentation, while supporting student participation and public engagement in the arts. He said his approach will “emphasize collaboration, clarity, and sustainability, reflecting MIT’s distinctive integration of the arts with science and technology.”

Makan came to MIT in 2006 as an assistant professor of music. From 2018 to 2024, he served as head of the Music and Theater Arts (MTA) Section in the School of Humanities, Arts, and Social Sciences (SHASS). In 2023, he was appointed associate dean for strategic initiatives in SHASS, where he helped guide the school’s response to recent fiscal pressures and led Institute-wide strategic initiatives.

With colleagues from MTA and the School of Engineering, Makan helped launch a new, multidisciplinary graduate program in music technology and computation. He was intimately involved in the project to develop the new Edward and Joyce Linde Music Building (Building 18), a state-of-the-art facility that opened in 2025. 

Makan was a member of the Future of the Arts at MIT Committee and chaired a working group on the creation of a center for the humanities, which ultimately became the MIT Human Insight Collaborative (MITHIC), one of the Institute’s strategic initiatives. Since last year, he has served as MITHIC’s faculty lead. Under his leadership, MITHIC has awarded $4.7 million in funding to 56 projects across 28 units at MIT, supporting interdisciplinary, human-centered research and teaching.

Trained initially as a violinist, Makan earned undergraduate degrees in music composition and religion from Oberlin and a PhD in music composition from the University of California at Berkeley.

A critically-acclaimed composer, Makan is the recipient of a Guggenheim Fellowship and the Luciano Berio Rome Prize from the American Academy in Rome. His music has been recorded by the Kronos Quartet, the Boston Modern Orchestra Project, and the International Contemporary Ensemble, and performed at Carnegie Hall, the Lincoln Center for the Performing Arts, and Tanglewood. His opera, “Persona,” premiered at National Sawdust and was performed at the Isabella Stewart Gardner Museum in Boston and by the Los Angeles Opera. The Los Angeles Times described the music from “Persona” as “brilliant.”

Makan succeeds Philip Khoury, the Ford International Professor of History, who served as vice provost for the arts from 2006 before stepping down in 2025. Khoury will return to the MIT faculty following a sabbatical.

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