Shares of UnitedHealth Group are surging before the market open Friday as Warren Buffett's Berkshire Hathaway disclosed that it recently purchased shares of the beleaguered insurer.

Beaten-down UNH is set to challenge its 50-day moving average after a major vote of confidence from the Oracle of Omaha.

TheStreet. Warren Buffett is arguably the most successful investor of all time. He's amassed an amazingly massive net worth by buying and usually holding stocks for the long haul. Trained under legendary value fund investor Benjamin Graham,