San Francisco. -- Software giant Microsoft has agreed to pay $1.2 billion to acquire Yammer, the San Francisco-based developer of private social networks for businesses designed to help employees more easily collaborate, The Wall Street Journal reported on Friday, citing a person familiar with the matter. Neither company has publicly confirmed the deal. The acquisition would bolster Microsoft's cloud computer offerings, as well as expand the company's reach into the corporate IT market. The news comes more than three months after Yammer raised $85 million in its fifth round of funding, led by DFJ Growth. The company has raised $142 million since its inception.