NSA contractor leaked US hacking tools by mistake, Kaspersky says

User downloaded malware while pirating Microsoft Office before running virus scan on machine containing confidential software, says Russian firm's founder

An incredible sequence of security mistakes led to a US National Security Agency contractor leaking his own confidential hacking tools to Russian cybersecurity firm Kaspersky Lab, the Moscow-based company has alleged.

The claim comes as part of an internal investigation into allegations that the company helped Russian spies discover and steal the NSA files, by locating and flagging the contractor.