Zero-fee stock trading app Robinhood is completing a huge fund raise to fuel its attack on big brokerage firms that charge around $7 to $10 per trade. According to sources, the round is led by Yuri Milner investment vehicle DST Global and values the company at $1.3 billion. Robinhood declined to comment.

Robinhood got its start in 2013 by offering a way for younger, less wealthy users to start investing. It provides an easy-to-use app for free tracking and trading of stocks. Robinhood replaces the traditional brokerages like Scottrade and E*Trade who charge per trade to cover their brick-and-mortar franchise, sales staff, and marketing spend.

Since Robinhood instead employs a leaner engineering-focused team and doesn’t need physical locations, it can pass the savings on to customers and undercut competitors by charging no per trade fee.

Robinhood founders Baiju Bhatt (left) and Vladamir Tenev (right)

Robinhood has since built a platform that allow other developers to offer zero-fee trades in their own apps. Last year, it launched its primary revenue stream, a $10 per month premium Robinhood Gold option. That allows users to skip the three-day waiting period for deposits and make trades instantly, as well as borrow up to double the amount of money in their…