Details of Microsoft's backup plan are emerging in the wake of the company's decision to walk away from its three-month long Yahoo bid.

While a steady stream of rumors has captivated Silicon Valley and Wall Street alike, it appears one possible target for Microsoft may be its old friend Facebook.

According to a Wall Street Journal report, Microsoft approached Facebook about acquiring the social network. Last October, Microsoft spent $240 million for a 1.6 percent stake in Facebook.

Both Facebook and Microsoft declined to comment on the rumors.

Meanwhile, Facebook continues to lure away top talent from Microsoft's key rival Google.