An ongoing study by Northeastern University and the University of Massachusetts claims that Sprint is arbitrarily throttling Microsoft’s Skype without adequately informing consumers. The findings come courtesy of David Choffnes, assistant professor of computer and information science at Northeastern. Choffnes developed an app named Wehe that he’s been using to track how wireless carriers are treating user data in the wake of the repeal of net neutrality rules last June. Choffnes and his team analyzed more than 719,417 tests conducted by 100,000 users across 135 countries, and discovered that wireless carriers routinely throttle streaming video applications. While carriers often claim this kind of throttling only occurs in response to network congestion, evidence suggests the practice is often tied to efforts to upsell users to pricier plans. Verizon, for example, now offers users three different tiers of “unlimited” data plans, but restricts video to 480p unless users are willing to shell out more money to remove this arbitrary limit. Sprint has previously come under fire for throttling games and music unless users paid more.

Image: Dave Choffnes

Artificial network restrictions designed specifically to help carriers make more money is precisely the sort of behavior net neutrality rules were supposed to prevent. It’s not just video that’s being treated arbitrarily, Choffnes found. His latest analysis of Wehe data found that Sprint and its prepaid wireless subsidiary Boost Mobile are also artificially restricting Skype performance over the company’s networks. This throttling occurred in 34 percent of 1,968 full tests run between January 18 and October 15 of this year.

“We did not find that throttling was limited to certain times of day or geographic locations,” Choffnes told Motherboard. “However, we did find that throttling used a fixed bandwidth limit shared by many users across the country, indicating that the amount of bandwidth given during throttling did not respond dynamically to congestion.” In other words, Sprint’s throttling does not appear to be a direct response to handling heavy traffic on the network. Yet some Sprint users might find their Skype video calls operating at a lower quality all the same, something he says isn’t clearly disclosed by the carrier.

“We could not find Skype throttling disclosed anywhere on their site,” Choffnes told me.

The FCC’s 2015 net neutrality rules allowed ISPs to engage in network management to handle network congestion—provided they were transparent about it. While the Ajit Pai FCC says it still expects ISPs to be transparent with consumers about the kind of connection they’re buying, those requirements are entirely voluntary and can now be ignored by ISPs without repercussion.

With the FCC no longer interested in forcing ISPs to be transparent, researchers like Choffnes say they hope to fill the void with crowdsourced research and a healthy dose of public shaming. Sprint denied throttling Skype when contacted by Motherboard.

“Sprint does not single out Skype or any individual content provider in this way,” a Sprint spokesperson told Motherboard. “The methodology used by the researchers is unclear and unproven, and there are many factors that may impact results on third-party apps” the company added.

Choffnes told Motherboard he remains confident in his findings despite Sprint’s denial. He also noted that the entire point of net neutrality was to prevent broadband providers from being able to limit services that potentially compete with their own offerings.

“In a neutral network, all of these services can compete on a level playing field to offer a product that attracts the most users,” he said. “When an Internet provider targets a service for throttling, the playing field can tilt in favor of one service over another.” “This is particularly problematic if the Internet provider's service is favored, because they can use this advantage to drive users away from competing products and to ones belong to the Internet provider,” Choffnes added. “And because the competition is limited by the Internet service they are given, in some cases there may nothing they can do to regain equal footing.”

While net neutrality rules died last June, most ISPs have tried to be on their best behavior in the months since—wary of adding any fuel to the fire ahead of next February’s court battle over the FCC’s repeal. Should the FCC lose that case, the agency’s 2015 rules have a good shot of being restored.