Hackers have managed to breach computer networks belonging to the company which runs the Nasdaq Stock Market.
According to The Wall Street Journal, people familiar with the situation revealed that hackers managed to penetrate the Nasday OMX Group's network repeatedly over the past year but failed to breach the part of the system that controlls the stock exchange's trading platform.
The FBI and other security agencies are said to be investigating the breach.
The sources said that the hackers seem to have just been "looking around", and did not tamper with anything.
Investigations into the breach revealed that hackers had accessed the Directors Desk communication tool, but Nasdaq OMX confirmed that no data was stolen.
“Through our normal security monitoring systems we detected suspicious files on the U.S. Servers. The files were immediately removed and at this point there is no evidence that any Directors Desk customer information was accessed or acquired by hackers,” Nasdaq OMX said in a statement.