Wall Street played its own version of war games on Thursday, testing its defenses against simulated cyberattacks bent on taking down U.S. stock exchanges. A total of 500 people took part in the exercise, called Quantum Dawn 2, in offices across 50 financial institutions and government agencies. The simulation included distributed denial of service (DDoS) attacks aimed at online banking sites. The players also had to counter a malware infection that threatened to take down trading operations, according to a security consultant. The test was part public relations to ease concerns customers may have about security in their financial institutions.”]