A US jury has found Microsoft violated a Uniloc patent used to protect against software piracy and has awarded Uniloc $388m, double the estimated damages caused by infringing the patent.

Uniloc makes software that prevents the creation, distribution and use of unauthorised copies of software. The company had accused Microsoft of infringing on a patent in the anti-piracy software registration system Microsoft uses as part of its product activation system.

The decision is a reversal of an earlier judgement in which the US District Court for the District of Rhode Island found in favour of Microsoft that no infringement had occurred.

Neither Uniloc nor Microsoft could immediately be reached for comment.