<p> The report cited people familiar with the matter as saying law enforcement investigators were considering a range of motives for the hacking, from financial gain to theft of trade secrets to a national security threat to damage the important stock exchange.</p>.<p> Authorities rank stock exchanges up with power companies and air traffic control centers as critical to the basic infrastructure of the United States.</p>.<p> The probe into the hacking at New York-based Nasdaq OMX Group Inc was started by the U.S. Secret Service and now includes the Federal Bureau of Investigation, the WSJ said.</p>.<p> A spokesman for Nasdaq OMX Group declined immediate comment on the report.</p>.<p> The WSJ said investigators have been unable to track the hacking to any specific individual or country.</p>.<p> "So far, (the perpetrators) appear to have just been looking around," the Wall Street Journal quoted one unidentified person involved in the Nasdaq case.</p>.<p> It reported that 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 so far not taking anything or tampering with anything.</p>
<p> The report cited people familiar with the matter as saying law enforcement investigators were considering a range of motives for the hacking, from financial gain to theft of trade secrets to a national security threat to damage the important stock exchange.</p>.<p> Authorities rank stock exchanges up with power companies and air traffic control centers as critical to the basic infrastructure of the United States.</p>.<p> The probe into the hacking at New York-based Nasdaq OMX Group Inc was started by the U.S. Secret Service and now includes the Federal Bureau of Investigation, the WSJ said.</p>.<p> A spokesman for Nasdaq OMX Group declined immediate comment on the report.</p>.<p> The WSJ said investigators have been unable to track the hacking to any specific individual or country.</p>.<p> "So far, (the perpetrators) appear to have just been looking around," the Wall Street Journal quoted one unidentified person involved in the Nasdaq case.</p>.<p> It reported that 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 so far not taking anything or tampering with anything.</p>