According to a report from The Indian Express, China-based hackers broke into the computer systems of India's Eastern Naval Command, where India's first nuclear submarine is undergoing trials. Using a virus transmitted by USB thumb drives (which are banned from Indian Navy offices), the hackers were able to cache information that matched keywords and transfer it to another thumb drive when one became available. That allowed the data to be moved to Internet-connected PCs, where the virus then dumped the data and transmitted it across the Internet to servers in China.

The virus is similar to one that attacked the US military's classified networks in 2008. Those led to a Department of Defense ban on the use of USB drives and any other writable removable media. The DOD partially lifted the ban in 2009, restricting the use of USB drives to "carefully controlled circumstances."

The Indian Navy has not revealed the extent of the hack, or how long it went on for. The Indian Express reports that at least six officers have been charged with "procedural lapses" that allowed the hack to happen.