Activist hedge fund Elliott Management has purchased a 15.3 percent stake in Gigamon, which makes software to manage traffic online, according to a 13-D filing Monday with the Securities and Exchange Commission. Elliott is run by billionaire investor Paul Singer, who just last week raised more than $5 billion in 24 hours. The firm said in the SEC filing that shares of Gigamon are "significantly undervalued and represent an attractive investment opportunity." Further, Elliott seeks to engage in a dialogue with Gigamon's board to discuss opportunities that would maximize shareholder value, the filing said. This could entail Elliott...