Exchange operators have faced their own computer intrusions. CME Group Inc. in November revealed that its ClearPort clearing system had been breached and some customer information was compromised. In 2011, Nasdaq OMX Group Inc. said it found suspicious files on a website it runs that lets corporate board members communicate with each other.
Cybersecurity has been flagged as one of the biggest threats to markets and governments by industry groups and regulators. A World Federation of Exchanges study in July found that computers at about 53 percent of exchanges around the world were attacked during the previous year.
In April, the Securities and Exchange Commission published a risk alert and started soliciting information from some of the biggest broker-dealers on their efforts to protect their technology from hackers.