Users browsing the web through one of AT&T's WiFi hotspots recently may have noticed a few extra ads online.
The company was using its WiFi service to inject ads on top of those that websites already run, according to Stanford University computer science Ph.D. candidate and lawyer Jonathan Mayer, who said in a blog post that he'd discovered unusual ads while browsing the web at Washington Dulles International Airport on AT&T's free WiFi.
"The web had sprouted ads," he wrote in the blog post on Tuesday. "Lots of them, in places they didn't belong .... Last I checked, Stanford doesn't hawk fashion accessories or telecom service. And it definitely doesn't run obnoxious ads that compel you to wait."
It wasn't clear whether marketers specifically paid for hotspot injection ads or whether AT&T was serving ads it had sold more generally.
Mr. Mayer suggested that the hotspot ads might violate the Federal Communications Commission's net neutrality rules, but Ars Technica said that "making that case might be tricky":
Inserting ads isn't the same as degrading traffic as long as customers can move past the ads and get to the actual website, noted Harold Feld, senior VP of advocacy group Public Knowledge. "It just looks like an ad-supported access network," he told Ars.
Mr. Mayer said he found that the ad injection platform comes from a startup called RaGaPa, which promises "Wi-Fi monetization and in-browser user engagement solutions."
AT&T isn't the only company to have done this. Comcast in 2014 began serving ads to devices connected to its WiFi hotspots. Some hotels have even been said to inject ads on top of the WiFi they charge guests for.
AT&T said it was only trying to find a way to support its free WiFi service. "Our industry is constantly looking to strike a balance between the experience and economics of free Wi-Fi," the company said in a statement. "We trialed an advertising program for a limited time in two airports (Dulles and Reagan National) and the trial has ended. The trial was part of an ongoing effort to explore alternate ways to deliver a free Wi-Fi service that is safe, secure and fast."
The company didn't answer questions about when the trial was started or how long it had been active.