NEW YORK (Reuters) -The U.S. Securities and Exchange Commission on Tuesday sued Virtu Financial, a broker-dealer that handles 25% of all market orders placed by retail investors in the U.S., for misleading customers into believing it properly safeguarded their confidential information. In a complaint filed in federal court in Manhattan, the SEC said Virtu repeatedly and falsely told customers that it used "information barriers" and "systemic separation between business groups" to protect their material nonpublic information. The SEC said that, in reality, "anyone...