Microsoft will not include a new feature recently recognised as a security risk in the first release of its new operating system, Vista.

Last week, just days after a beta of Windows Vista was released, an Austrian hacker claimed to have devised a series of viruses that targeted the Monad command shell and could be used to disrupt a system.

However, Microsoft has since confirmed that it will not include the shell in the first public version of Vista, expected at the end of 2006.

The Monad Shell lets users access the operating system using text-based commands rather than the traditional Windows graphical user interface. In the past, Microsoft has said that Monad will be part of Longhorn, the code name for both the next client and server versions of Windows.

Monad is expected to be included in Windows over the next "three to five years," though, according to Microsoft's director of product management, Eric Bergsaid. "Our intention is to synchronise it with both client and server operating systems," he said.

Security experts had worried that if Monad were to be included in a widely used client, it might become an attractive target for hackers, especially if the shell were to be enabled by default. Whether it will be enabled by default is unclear. "There are multiple ways that we could introduce this technology to the client stream," Berg said.

The first Microsoft product to use Monad will be the next release of Microsoft's Exchange messaging server, codenamed Exchange 12, which is due in 2006. Monad is then expected to be included in the Windows Server "Longhorn", expected in 2007, and then could be available in a future Windows Vista release, said Rob Helm, director of research with Directions on Microsoft. "Presumably, as time goes on, all of Microsoft's products will have Monad scripting interfaces," he said.