Hackers have repeatedly penetrated the computer network of the company that runs the Nasdaq Stock Market during the past year, and federal investigators are trying to identify the perpetrators and their purpose, according to people familiar with the matter.
The exchange's trading platform—the part of the system that executes trades—wasn't compromised, these people said. However, it couldn't be determined which other parts of Nasdaq's computer network were accessed. ...
"So far, [the perpetrators] appear to have just been looking around," said one person involved in the Nasdaq matter.
--Devlin Barrett, WSJ, on the cyber-vulnerability of our core infrastructure