"Banging the close" and "spoofing" are two trading practices prohibited by the Dodd-Frank Act and the Commodity Futures Trading Commission is working to better define them. SIFMA and the International Swaps and Derivatives Association wrote to the commission earlier this year to raise concerns about such terms. "These terms lack definition, which makes them susceptible to being interpreted to sweep in a range of completely appropriate conduct," the associations wrote. Commission Chairman Gary Gensler said the agency's staff is also working on a proposal to assess and oversee algorithmic trading. Read SIFMA's comment letter.