Basically: Athena targeted stocks with closing time imbalances between buys and sells, where NASDAQ ran a special order routing process, and traded with itself to influence the price reported at market close.
The dollar amounts the SEC describes are insignificant (that's obviously not a defense for the firm charged with the behavior).
http://www.sec.gov/litigation/admin/2014/34-73369.pdf
Basically: Athena targeted stocks with closing time imbalances between buys and sells, where NASDAQ ran a special order routing process, and traded with itself to influence the price reported at market close.
The dollar amounts the SEC describes are insignificant (that's obviously not a defense for the firm charged with the behavior).