In an email sent on Monday afternoon to all Microsoft employees, Satya Nadella, Senior Vice-President of research and development for Microsoft's online services division, invited staffers to begin testing the Kumo search engine, currently only available on the company's internal network, the ‘Wall Street Journal’ reported.

For now, Microsoft's Live Search, at live.com, remains the company's search engine for the public.

A person familiar with the matter was quoted as saying that Microsoft hasn't decided yet whether to rebrand Live Search as Kumo, which Nadella refers to as a code name in his email.

Kumo in Japanese means spider, a reference to so-called spider software that crawls from website to website, adding the data to vast search-engine indexes, the paper said.