Companies Can Build Accurate User Profiles from Online History, Mozilla Research Finds

• Users are sometimes tracked online despite no-track options
• Online profiles are accurate most of the time
• Large companies can build online profiles with little available data

Advertisers can quickly identify users from their online profiles by using data collected from browsing history, new research from Mozilla showed.

Despite the implementation of aggressive features in an Internet browser that should prevent user tracking, companies find new ways to identify users as soon as they go online. “Why We Still Can”t Browse in Peace:On the Uniqueness and Reidentifiability of WebBrowsing Histories” is a new study from Mozilla that examines online tracking once again after releasing a similar paper in 2012.

The original research found it”s possible to identify users from their online activity with great effectiveness. It”s easy to imagine that things have changed over the past decade, but Mozilla”s latest number shows that”s not the case.

“Our dataset consists of two weeks of browsing data from ~52,000 Firefox users,” say the researchers. “Our work replicates the originalpaper”s core findings by identifying 48,919 distinct browsing profiles, of which 99% are unique.”

“High uniqueness holds even when histories are truncated to just 100 top sites. We then find that for users who visited 50 or more distinct domains in the two-week data collection period, ~50% can be reidentified using the top 10k sites. Reidentifiability rose to over 80% for users that browsed 150 or more distinct domains,” they continue.

Mozilla used data from 52,000 users who agreed to participate in the experiment. The results are interesting and worrying at the same time, as it discovered that 99% of the profiles identified are unique to each user.

When third-party tools are introduced, from Google and Facebook, the situation becomes even more complicated. Large companies gather data all the time, building detailed profiles that are highly accurate. In a worst-case scenario, all of this private data could end up for sale.

Unfortunately, users have few options to mitigate their exposure, besides always using the “no-track feature” in browsers and keeping an eye out for data breaches that could expose much of their private life.