In October 2014, a junior IT worker sitting at his desk in Moscow noticed something strange on his computer. Kaspersky Labs, the Russian cyber security company he worked for, had accessed sensitive data taken from a computer in Baltimore, thousands of miles away from its offices but a stone’s throw from the headquarters of America’s spying organisation, the National Security Agency.

These were not just a random customer’s files, but classified documents belonging to an American spy. What should have been a routine retrieval of the information set in motion a series of events that could prove catastrophic for the company.

The US government now claims Eugene Kaspersky, the Russian businessman and cyber security tycoon who founded the company, has worked with the Kremlin to allow unprecedented access to NSA employees’ computers, exposing their own arsenal of top-secret hacking tools.