Websites of the NASDAQ and BATS stock exchanges as well as the Chicago Board Options Exchange (CBOE) knocked offline for parts of Monday and Tuesday after coming under a sustained online attack by a group with links to Anonymous. A group calling itself LONGwave99 claimed credit for the attacks, which were dubbed Operation Digital Tornado in a post on the Web site Pastebin.com on Sunday and through a Twitter account. The group said it was acting in support of the 99% movement a possible reference to the Occupy Wall Street movement.
Source: https://threatpost.com/anonymous-linked-attacks-hit-us-stock-exchanges-021512/76216/