The report provides steps to identify the malicious software used by criminal hackers that went undetected by anti-virus software when it infected Target's network, according to Tiffany Jones, a senior vice president with the security intelligence firm iSIGHT Partners, which helped draft the document.

"This report was generated so that we could get it into the hands of commercial entities so that they had information they needed to protect themselves," she told Reuters in an interview.

(Reporting by Jim Finkle; Editing Richard Valdmanis)