The New York Stock Exchange slapped Credit Suisse with a fine on Wednesday for failing to supervise one of its trading algorithm — the first time the stock exchange has disciplined a firm for algo infractions.

On Nov. 14, 2007, the program halted traffic at five different trading posts on the NYSE floor after a Credit Suisse trader changing a set of orders initiated by the program manually double-clicked the mouse around 3:40 p.m. Because of the gap in time between the first and second mouse clicks, the program was not able to completely cancel earlier requests. SmartWB instead sent out roughly 600,000 “cancel-replace” messages, prompting the NYSE’s electronic order system to send out 405,000 “reject-unmatched cancel” messages, swamping traffic and delaying closing at the posts for nearly half an hour. And because the program had no error alerts, Credit Suisse did not find out about the messages until the following day. [Source]