FBI is probing a computer-security breach targeting Citibank that resulted in a theft of tens of millions of dollars by hackers who appear linked to a Russian cyber gang, according to a media report.
The Wall Street Journal in a news report said the attack underscores the blurring of lines between criminal and national-security threats in cyber space.
Hackers also assaulted two other entities, at least one of them a US government agency, said people familiar with the attack on Citibank, the daily reported.
Currently the federal government has 27 percent stake in Citigroup, parent company of the Citibank.
The threat was initially detected by US investigators who saw suspicious traffic coming from Internet addresses that had been used by the Russian Business Network, a Russian gang that has sold hacking tools and software for accessing US government systems.
The group went silent two years ago, but security experts say its alumni have re-emerged in smaller attack groups, the report said.
"Security officials worry that, beyond stealing money, hackers could try to manipulate or destroy data, wreaking havoc on the banking system. When intruders get into one bank, officials say, they may be able to blaze a trail into others," the report said.
The daily said one Robert Blanchard, co-owner of a lighting company in Mount Vernon, New York said that someone hacked into his Citibank account and stole over $1 million.
The bulk of the money was recovered later.
"After days of prodding, Citibank sleuths began working to help him recover $810,855 from the Latvian bank, and Citibank then gave him the remainder," the daily said.