Microsoft inadvertently shipped the Nimda virus in its Korean version of Visual Studio .NET. The virus was embedded in a compiled Help file, which the company had received from a Korean sub-contractor. Microsoft said it hadn't scanned the Help file thoroughly, and the virus remained undetected until the product had already shipped. A Microsoft employee subsequently detected the virus. Microsoft released the article "PRB: Inert Virus Found in Korean Language Version of Visual Studio .NET," which explains the problem in detail and offers a patch that removes the virus from a hard-disk installation.