South Korea's securities firms posted a record quarterly net profit of 4.33 trillion won ($2.63 billion) in the first quarter this year, driven by a surge in stock trading activity, Financial Supervisory Service data showed Friday. According to the FSS's provisional operating results, the combined net profit of 61 brokerages rose 77.1 percent on-year to 4.33 trillion won in the January-March period from 2.44 trillion won a year earlier. The figure more than doubled from 1.86 trillion won in the