A trader pauses amidst the activity in the S&P 500 pit at the Chicago Mercantile Exchange, October 26, 1998 REUTERS/Sue Ogrocki Commodities trader Navinder Singh Sarao has been arrested at his home in London in connection with the 2010 "Flash Crash" that rocked global markets.

On May 6, 2010, the market mysteriously plunged 9%. The Dow fell about 1,000 points. Since then the SEC has released reports on the matter but really no one has been blamed.

The agency said it was likely the fault of a single trader manipulating S&P futures contracts, but no one was ever identified.

Until today.

According to the CFTC, Sarao spoofed S&P futures, called "E-Minis," from 2010 to 2014.

Celiza Bragança, a securities-fraud lawyer at Stoltmann Law in Chicago, defines spoofing as "placing orders out in the market in order to manipulate the price -- in order to move the price -- with the expectation that you will be placing orders on the other side of that order, to benefit from a temporary price movement that you have created."

The CFTC says that Sarao's spoofing tactics were "exceptionally large, aggressive, and persistent," leaving one to wonder how he wasn't caught before.

Sarao used a special algorithm called a "layering algorithm" to push out multiple large sell orders that would modify themselves to move with the E-Minis price. Allegedly, the layers of orders would increase the spread between bid and the asking price so that other traders would stay away from the best price. Sarao would then cancel the sell orders, according to the CFTCs complaint.

From the release (emphasis added):

[In] or about June 2009, Defendants modified a commonly used off-the-shelf trading platform to automatically simultaneously “layer” four to six exceptionally large sell orders into the visible E-mini S&P central limit order book (the Layering Algorithm), with each sell order one price level from the other. As the E-mini S&P futures price moved, the Layering Algorithm allegedly modified the price of the sell orders to ensure that they remained at least three or four price levels from the best asking price; thus, remaining visible to other traders, but staying safely away from the best asking price. Eventually, the vast majority of the Layering Algorithm orders were canceled without resulting in any transactions. According to the Complaint, between April 2010 and April 2015, Defendants utilized the Layering Algorithm on over 400 trading days.<

Check out the full CFTC press release below:

The CFTC Complaint Alleges that Defendants’ Manipulative Conduct Contributed to the Market Conditions that Led to the May 6, 2010 Flash Crash

Washington, DC – The U.S. Commodity Futures Trading Commission (CFTC) today announced the unsealing of a civil enforcement action in the U.S. District Court for the Northern District of Illinois against Nav Sarao Futures Limited PLC (Sarao Futures) and Navinder Singh Sarao (Sarao) (collectively, Defendants). The CFTC Complaint charges the Defendants with unlawfully manipulating, attempting to manipulate, and spoofing — all with regard to the E-mini S&P 500 near month futures contract (E-mini S&P). The Complaint had been filed under seal on April 17, 2015 and kept sealed until today’s arrest of Sarao by British authorities acting at the request of the U.S. Department of Justice (DOJ). After the arrest, the DOJ unsealed its own criminal Complaint charging Sarao with substantively the same misconduct.

The Standard & Poor’s 500 Index is an index of 500 stocks designed to be a leading indicator of U.S. equities. The E-mini S&P 500 is a stock market index futures contract based on the Standard & Poor’s 500 Index and is one of the most popular and liquid equity index futures contracts in the world. The contract is traded only at the Chicago Mercantile Exchange (CME).

According to the Complaint, for over five years and continuing as recently as at least April 6, 2015, Defendants have engaged in a massive effort to manipulate the price of the E-mini S&P by utilizing a variety of exceptionally large, aggressive, and persistent spoofing tactics. In particular, according to the Complaint, in or about June 2009, Defendants modified a commonly used off-the-shelf trading platform to automatically simultaneously “layer” four to six exceptionally large sell orders into the visible E-mini S&P central limit order book (the Layering Algorithm), with each sell order one price level from the other. As the E-mini S&P futures price moved, the Layering Algorithm allegedly modified the price of the sell orders to ensure that they remained at least three or four price levels from the best asking price; thus, remaining visible to other traders, but staying safely away from the best asking price. Eventually, the vast majority of the Layering Algorithm orders were canceled without resulting in any transactions. According to the Complaint, between April 2010 and April 2015, Defendants utilized the Layering Algorithm on over 400 trading days.

The Complaint alleges that Defendants often cycled the Layering Algorithm on and off several times during a typical trading day to create large imbalances in the E-mini S&P visible order book to affect the prevailing E-mini S&P price. Defendants then allegedly traded in a manner designed to profit from this temporary artificial volatility. According to the Complaint, from April 2010 to present, Defendants have profited over $40 million, in total, from E-mini S&P trading.

As alleged in the Complaint, Defendants were exceptionally active in the E-mini S&P on May 6, 2010, commonly known as the Flash Crash Day. On the afternoon of that day, the E-mini S&P market price suffered a sharp decline, followed shortly thereafter by sharp declines in the prices of other major U.S. equities indices and individual equities. After a few minutes, markets quickly rebounded to near previous price levels. According to the Complaint, Defendants utilized the Layering Algorithm continuously, for over two hours, immediately prior to the precipitous drop in the E-mini S&P price, applying close to $200 million worth of persistent downward pressure on the E-mini S&P price. According to the Complaint, Defendants’ manipulative activities contributed to an extreme E-mini S&P order book imbalance that contributed to market conditions that led to the Flash Crash.

The Complaint further alleges that Defendants engaged in a variety of other manual spoofing techniques whereby Defendants allegedly would place and quickly cancel large orders with no intention of the orders resulting in transactions. At times, according to the Complaint, this manual spoofing was used to exacerbate the price impact of the Layering Algorithm.

CFTC Director of Enforcement Aitan Goelman commented: “Protecting the integrity and stability of the U.S. futures markets is critical to ensuring a properly functioning financial system. Today’s actions make clear that the CFTC, working with its partners on the criminal side, will find and prosecute manipulators of U.S. futures markets wherever they may be.”

In its ongoing litigation, the CFTC is seeking permanent injunctive relief, disgorgement, civil monetary penalties, trading suspensions or bans, and payment of costs and fees.

As noted above, the U.S. Department of Justice filed a related criminal action charging Sarao with manipulation, attempted manipulation, spoofing, and wire fraud on February 11, 2015, in the U.S. District Court for the Northern District of Illinois. In conjunction with that action, the Federal Bureau of Investigation (FBI), with the assistance of Scotland Yard and the U.K.’s Financial Conduct Authority (FCA), took Sarao into custody today, at his residence in London. Sarao awaits extradition to the United States on these charges.

Given Defendants’ ongoing unlawful conduct and the potential for dissipation of Defendants’ ill-gotten gains, on April 17, 2015, U.S. District Judge Andrea R. Wood issued an Order freezing and preserving assets under Defendants’ control and prohibiting them from destroying documents or denying CFTC staff access to their books and records. The Court has scheduled a hearing for May 1, 2015, on the CFTC’s motion for a preliminary injunction.

The CFTC thanks and acknowledges the assistance of the CME, the U.S. Department of Justice, the FBI, the FCA, Scotland Yard, and the Securities and Exchange Commission.

CFTC Division of Enforcement staff members responsible for this matter are Jeff Le Riche, Jo Mettenburg, Jenny Chapin, Jessica Harris, Allison Sizemore, Carlin Metzger, Elizabeth Padgett, Mary Lutz, Jeri Cobb, Jordon Grimm, and Charles Marvine.

More to come.