NEW YORK, Dec 3 (Reuters) - Virtu Financial will pay a $2.5 million fine to settle U.S. Securities ​and Exchange Commission accusations the large market maker ‌improperly allowed almost all employees at its broker-dealer unit access to ‌confidential information about customers and their trades. The broker-dealer unit Virtu Americas, which according to the SEC handled about 25% of market orders from U.S. retail investors during the relevant ⁠period, did not ‌admit or deny wrongdoing, the SEC said on Wednes ...