Warren Buffett’s Berkshire Hathaway Inc. added to its stake in the internet domain-name-registry company VeriSign Inc. in the final week of the year, according to a regulatory filing.

Geico, and pension plans of other Berkshire Hathaway units bought nearly $30 million of shares of domain-name registry firm VeriSign.

Warren Buffett is one of the most successful investors in history. He has often recommended that most people invest in an S&P 500 index fund. The Vanguard S&P 500 ETF is a popular choice that Buffett himself owns through his company,

Warren Buffett’s Berkshire Hathaway Inc. has been busy over the past week buying stock in an internet domain-name registry company, to extend its stature as the company’s largest shareholder.