Hackers repeatedly made their way into the computer network that runs the Nasdaq Stock Market during the past year. The part of the system that executes trades was not breached but other parts of Nasdaq's infrastructure were accessed, though it's still unclear which ones. The Secret Service and Federal Bureau of Investigation are looking into the matter, though they haven't found any malicious activity yet, according to The Wall Street Journal:

"So far, [the perpetrators] appear to have just been looking around," said one person involved in the Nasdaq matter. Another person familiar with the case said the incidents were, for a computer network, the equivalent of someone sneaking into a house and walking around but—apparently, so far—not taking or tampering with anything.

Unsurprisingly, Nasdaq has not commented on the report. Investigators are worried that they still have not been able to figure out the hackers' motives nor are they confident that they've been able to plug all potential security holes. Furthermore, not only are the hackers identities still unknown, but officers still have not been able to figure out what country the hacks were initiated from. Some evidence points towards Russia, but the person or people responsible could be simply using computers in that country as a conduit.