Knight Capital Group Inc. faced growing pressure to find a savior as clients from Citigroup Inc. to Vanguard Group Inc. curtailed business with the firm following a software bug that triggered a $440 million loss. Knight, one of the biggest American market makers for stocks, is exploring strategic and financial alternatives as the malfunction cost the company almost four times what it earned last year. The firm’s shares lost 75 percent in two days after the faulty software flooded the market with unintended trades, sending dozens of stocks into spasms.
