Page 4 summarizes all that really needs to be said here: <a href="http://www.sec.gov/litigation/admin/2013/34-70694.pdf" rel="nofollow">http://www.sec.gov/litigation/admin/2013/34-70694.pdf</a><p>Knight didn't have a proper risk system. A correct risk system is a dead-man switch. There is just no way to place this many erroneous orders and get them filled. Capital Limits Exceeded: Full Shutdown. Risk System Crashes: Full shutdown. Heartbeat fails: Full shutdown.<p>Better to have a paranoid risk system than a rouge strategy.<p>The real flaw wasn't legacy code, it was straight-up laziness. This really isn't rocket-science.