In what has been termed the world's biggest cyber spy ring, the Chinese hackers used simple methods of e-mail and Twitter to steal secrets from computers around the world, says the report 'Shadows in the Cloud: An investigation into cyber espionage 2.0'' released here Tuesday.

In their year-long investigations, the researchers recovered India's national security files carrying information about the anti-aircraft, surface-to-air Pechora missile project, the Iron Dome missile system, and the artillery's Project Shakti.