A hacking attack on the US Nasdaq stock exchange could have been the work of a foreign government, a former insider says, as America's top electronic intelligence service the National Security Agency (NSA) joins the probe.
Joel Brenner, the former head of US counterintelligence under both Bush and Obama administrations, told business news site Bloomberg: "Bringing in the NSA... means they think they're either dealing with a state-sponsored attack or it's an extraordinarily capable criminal organisation."
The fact that the NSA has been called in to help the FBI and Nasdaq's enquiries into the October attack lends weight to speculation that the intrusion was more severe than at first thought, and may even have jeopardised America's financial system.
Investigators are yet to establish the motive behind a series of attacks on the US' second-largest stock exchange, which was first disclosed to Congress last month. Security experts suggest the NSA may be able to help by unscrambling encrypted messages sent by the hackers.
When Nasdaq first announced the breach, it was believed to have affected a single system known as the 'Directors Desk', and that no data or documents had been taken. Now it appears that intruders may have penetrated much deeper.
Uncertainty surrounding the attack could affect confidence in exchange operator Nasdaq OMX Group, says Alexander Tabb, a partner at financial market research firm Tabb Group.
"For an organisation like Nasdaq, it does have an impact on the overall perception of their security, their resiliency and their value," Tabb said. "For potential partners of the company, that has to be a concern."
More than 93 billion shares were traded on the Nasdaq exchange during the fourth quarter of 2010, equal to almost 20 per cent of the US equities market.
The FBI and Nasdaq declined to comment on the possibile repercussions of the attack.