One of the biggest concerns for tech users today is their data–what is collected, how it is used, and who it is shared with. To address this concern, the Electronic Frontier Foundation (EFF) recently published its Who Has Your Back? report, ranking tech companies on their willingness to share user data with the US government.

The EFF ranked the companies on a star-based system, awarding them a star for each of the categories measured. In the report, companies were ranked on whether they did the following: Followed industry-wide best practices, told users about government data requests, promised not to sell out users, stood up to national security letter (NSL) gag orders, and supported the reform of Section 702 to reduce data collection.

All of the companies studied followed industry best practices. However, only Adobe, Credo, Dropbox, Lyft, Pinterest, Sonic, Uber, Wickr, and WordPress received a star in every category.

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Many other companies fared much worse. Here are the six lowest performing companies on the EFF list:

1. AT&T

AT&T follows best practices well by publishing a transparency report and guidelines for government requests, and by requiring warrants for content, the report said. But, that’s the only star it received. In the report, the EFF urged AT&T to make strides in the other measures areas as well.

2. Comcast

Comcast also only got one star from the EFF, also for following best practices. Comcast has not called for reform to Section 702 and hasn’t promised not to sell out users, nor does it stand up to gag orders or let users know when the government is requesting data.

3. T-Mobile

This is T-Mobile’s first year in the EFF report, and it isn’t off to a good start. Much like the above companies, T-Mobile only earned a single star for its following of best practices. While the firm doesn’t promise not to sell out users, it does publicly state what data it shares with third-party services in its privacy policy, the report said.

4. Verizon

Verizon received its one star for best practices, but the EFF report said that “there is much room for improvement” for the company. The company’s privacy policy notes that it does share user data with vendors and partners, and “to comply with valid legal process.”

5. Amazon

Amazon has been on the EFF report for the past six years, but the firm only received two stars in 2017–one for following best practices and the other for supporting the reform of Section 702. Amazon still hasn’t clearly stated its policies regarding how third-parties access users data, nor has it explicitly forbidden them from using the data for surveillance, the report said.

6. WhatsApp

In its second year on the list, WhatsApp also earned the same two stars as Amazon–for both supporting Section 702 reform and following best practices. The company has stated that it does share information with “third-party providers,” but requires them to use it “in accordance with our instructions and terms or with express permission from you.”