UnitedHealth Group Inc. shares jumped after funds piled into the company, which has been hampered by a federal probe into its business practices and weakening results.

Shares of some of UnitedHealth’s peers got a bump in the wake of Berkshire’s investment in the healthcare giant, and they all look cheaper based on price relative to expected earnings.

Shares of UnitedHealth Group surged nearly 14% on Friday after billionaire Warren Buffett's Berkshire Hathaway bought 5 million shares of the company, providing a shot in the arm for investors who think the health conglomerate will turn around under its new CEO.

UnitedHealth just won't quit. Shares of the healthcare giant were up 13.5% in recent trade, building on their earlier gains. That leaves it on track for its biggest one-day jump since Oct. 13, 2008, when the stock rose 34.

Berkshire Hathaway's $1B+ UnitedHealth investment highlights confidence despite profit woes. Read why UNH offers attractive upside for long-term investors.

The cyberattack at UnitedHealth Group's tech unit last year impacted 192.7 million people, the U.S. health department's website showed on Thursday.

Even though Warren Buffett seems to think the value of UnitedHealth stock is about right, that doesn’t mean investors should ignore the long list of unresolved issues facing the company.

UnitedHealth Group ( UNH 12.04%) has been a solid dividend growth stock for years. Generally, its yield has been fairly low, due to the stock's rising value. Even as the healthcare insurance giant has grown its dividend, its yield hasn't been particularly high or noteworthy.