Former US Secretary of State Hillary Clinton has sounded the alarm on the threat of a Russian-waged information war waged for Western democracies in a speech in California on Friday.

Calling Russian information war, or influence operations, a "clear and present danger to our democracy", the former candidate for president gave the example of the use of social media accounts to stir up divisions over race and politics in the US in recent weeks.

"Make no mistake this isn't just about what happened in 2016, it's about what is happening right now," she said in a speech given at the Stanford Centre on Democracy, Development, and the Rule of Law.

Her address comes as the American public and lawmakers seek answers from Silicon Valley about the effect social media platforms had on US electoral politics.