Microsoft has finished developing a custom version of its Windows 10 operating system for the Chinese government. Microsoft worked with the China Electronics Technology Group (CTEC) on the joint venture, but the Wall Street Journal reports that the software giant isn’t revealing exactly what it has altered in the new custom version of Windows 10. China’s government previously banned Windows 8, citing security concerns, and launched an anti-monopoly probe against Microsoft.

The Chinese government has also been concerned over foreign software that could be used by the NSA to spy on activities, and has consistently tried to move away from relying on Microsoft’s Windows software. Back in 2013 it partnered with Ubuntu maker Canonical to create an alternative to Windows, codenamed Kylin. That effort failed, and a new Linux-based operating system dubbed NeoKylin is the latest attempt to create an alternative to Windows in China.

Microsoft has inked a number of deals in China to improve its position in the Chinese market, including partnerships with Tencent, Lenovo, and Xiaomi. This latest partnership will raise a number of questions around Microsoft's presence in China, especially around what exactly the company has altered in Windows 10 to satisfy the Chinese government.

The software maker has also tried to fight the large problem of software piracy in China, with activation software designed to prevent Windows from being pirated. Most software pirates have found ways around this activation software, and Windows piracy continues to be an issue in China.