Berkshire Hathaway continued its purchases of Verisign in recent days, buying about $4 million of the company that provides Internet domain registry and other services. The small recent buys, approximately 20,

Warren Buffett has invested more than $74 million in a Reston company best known for controlling internet domains for organizations across the globe.

VeriSign is ranked 5th in the S&P 500 for the highest profit margin, at about 56%, tied with Nvidia, according to third-quarter financial data.