"We are committed to building a community where people can feel safe making their voices heard." That's how Facebook's deputy chief privacy officer opened his public policy announcement on Monday, in a declaration aimed at users who fear that Facebook and others are mining their social data to track their behavior.。

"Today we are adding language to our Facebook and Instagram platform policies to more clearly explain that developers cannot 'use data obtained from us to provide tools that are used for surveillance,'" wrote Rob Sherman, the company's privacy officer.。

Sherman acknowledged that the policy shift came after some public prodding by California's ACLU branch, the Center for Media Justice, and Color of Change. In October, the ACLU of California exposed how social media surveillance companies such as Geofeedia used data provided by Facebook, Instagram and Twitter to track activists. The company then sold their services to police departments.。

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The revelation resonated, and Facebook (which owns Instagram) and Twitter cut off access to Geofeedia almost immediately. 。

“When technology companies allow their platforms and devices to be used to conduct mass surveillance of activists and other targeted communities, it chills democratic dissent and gives authoritarianism a license to thrive," Center for Media Justice Executive Director Malkia Cyril said in a statement lauding Facebook's announcement.。