The Obama administration is leading a global effort to deploy “shadow” Internet and mobile phone systems that dissidents can use to undermine repressive governments that seek to silence them by censoring or shutting down telecommunications networks.

Some projects, such as the Palisades project in Afghanistan, involve technology that the United States is developing; others pull together tools that have already been created by hackers in a “liberation-technology” movement sweeping the globe.

The Obama administration’s initiative is in one sense a new front in a longstanding diplomatic push to defend free speech and nurture democracy. But developers caution that independent networks come with downsides: repressive governments could use surveillance to pinpoint and arrest activists who use the technology or simply catch them bringing hardware across the border.

Creating simple lines of communication outside official ones is crucial, said Collin Anderson, a 26-year-old liberation-technology researcher.