Report: NSA joins Nasdaq hack probe

The National Security Agency has joined the investigation into last October's cyberattack on the computer network of the company that runs the Nasdaq stock exchange, according to a Bloomberg report that cited people familiar with the probe.

The top U.S. electronic intelligence agency will reportedly join efforts by the Secret Service and Federal Bureau of Investigations into a security breach at New York-based Nasdaq OMX Group. When the intrusions were revealed in February, it was thought that they had not compromised the tech-heavy exchange's trading platform, which executes investors' trades, but it was unknown which other sections of the network were accessed.

However, the intrusion was more extensive than Nasdaq previously disclosed, and it may take investigators months to determine which sections were accessed, Bloomberg reported.

The NSA probe is expected to focus on how far the attack reached and which other systems may have been breached, according to the report. The NSA's involvement may signal a concern that the attack poses a national security risk. Investigators are reportedly considering a range of other motives for the breach, including personal financial gain and theft of trade secrets.

Investigators had initially suspected the attack originated from Russia, but that turned out not to be the case, and investigators are still trying to determine the source of the attack, Bloomberg reported.

Nasdaq representatives did not immediately respond to requests for comment.

Nasdaq, which is thought to be as critical from a security standpoint as the national power grid or air traffic control operations, has been targeted by hackers before. In 1999, a group called "United Loan Gunmen" defaced Nasdaq's public Web site with a story headlined "United Loan Gunmen take control of Nasdaq stock market." The vandalism was quickly erased, and Nasdaq officials said at the time that the exchange's internal network was unaffected.