Activist investor Trian Fund Management takes stake in Comcast

Shares of Comcast gained sightly in after-hours trading Monday after Trian Fund Management took a stake in the cable giant. The hedge fund bought 7.16 million class A common share of Comcast, a regulatory filing showed. "Trian believes Comcast's stock is undervalued. We have recently begun what we believe are constructive discussions with Comcast's management team and look forward to continuing those discussions," a Trian spokesperson told CNBC. CNBC's David Faber reports.