Privacy advocates are pushing for stricter rules about how mobile carriers handle users’ wireless data.

While social media companies are often targeted for their handling of user data, wireless carriers have a treasure trove of information on their customers, including location data, internet usage, call history, texting history, and more. An FCC inquiry regarding the habits of the top 15 carriers in the US showed that data retention practices are “all over the map.”

That was the assessment of Harold Feld, senior vice president at digital privacy group Public Knowledge, according to The Seattle Times.

“The only ‘industry standard’ appears to be that there is no standard at all for how long carriers retain data, how they protect it, or how hard they make it for their customers to invoke their rights,” Feld added.

According to the Times, T-Mobile stores information on its customers, including their location data, for up to two years, while AT&T and its Cricket Wireless business store data for 13 months. Meanwhile, Verizon stores data for one year, and Mint Mobile stores data for 18 months.

The lack of standardization and accountability, not to mention the stakes involved, prompted strong words from FCC Chairwoman Jessica Rosenworcel:

“Our mobile phones know a lot about us. That means carriers know who we are, who we call, and where we are at any given moment,” said Rosenworcel. “This information and geolocation data is really sensitive. It’s a record of where we’ve been and who we are. That’s why the FCC is taking steps to ensure this data is protected.

“Today, I’m publishing the responses I received from mobile carriers on how they handle geolocation data to help shed light on this issue for consumers. Additionally, I have asked the Enforcement Bureau to launch a new investigation into mobile carriers’ compliance with FCC rules that require carriers to fully disclose to consumers how they are using and sharing geolocation data,” continued Rosenworcel. “Finally, if you, as a consumer, have concerns or complaints about how your provider is handling your private data, the FCC is making it easier for you to file complaints and make your concerns known—so we can take action under the law.”