The US National Security Agency has awarded a secret cloud computing contract worth up to US$10 billion to Amazon Web Services.

But the contract is already being challenged by Microsoft, which has filed a protest with the US Government Accountability Office.

The contract is code-named WildandStormy and represents the second multibillion-dollar cloud contract the US intelligence community has awarded in the past year.

Details on the NSA’s newly-awarded cloud contract are unknown, but the acquisition appears to be part of the NSA’s attempt to modernise its primary classified data repository, the Intelligence Community GovCloud.

NSA has previously moved its data, including signals intelligence and other foreign surveillance and intelligence information it ingests from multiple repositories around the globe.