One of the most popular measures of volatility is being manipulated, charges one individual who submitted a letter anonymously to the Securities and Exchange Commission and the Commodity Futures Trading Commission, MarketWatch reports.

The letter makes the claim to regulators that fake quotes for the S&P 500 index are skewing levels of the Cboe Volatility Index, which reflects bearish and bullish options bets 30-days in the future on the S&P 500 to gauge implied stock-market volatility (see excerpt from the letter below).