How to lose $172,222 a second for 45 minutes

Page 4 summarizes all that really needs to be said here: http://www.sec.gov/litigation/admin/2013/34-70694.pdf

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.

Better to have a paranoid risk system than a rouge strategy.

The real flaw wasn't legacy code, it was straight-up laziness. This really isn't rocket-science.

Date: 2013

Big discussion: https://news.ycombinator.com/item?id=6589508

Summary of Knight Frank high speed trading mishaps.