Jane Street has told staff it will contest a ban by India's financial regulator which has accused the U.S. high-frequency trading giant of market manipulation, adding that its practices in question were "basic index arbitrage trading".

At the heart of the controversy is Jane Street’s aggressive trading in the derivatives (futures) segment, where the firm executed trades designed not just to profit, but to sway the market itself. Here's how.

The lawsuit alleged that the traders had stolen a “ highly valuable, unique, and proprietary ” trading strategy, which was quickly revealed to revolve around India’s booming options market. Jane Street and Millennium settled the lawsuit in December, but judging from SEBI’s report it has cast a long (and expensive) shadow.