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’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.

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,