A hacker used a tiny Raspberry Pi computer to infiltrate NASA’s Jet Propulsion Laboratory network, stealing sensitive data and forcing the temporary disconnection of space-flight systems, the agency has revealed.

The April 2018 attack went undetected for nearly a year, according to an audit report issued on June 18, and an investigation is still underway to find the culprit.

A Raspberry Pi is a credit-card sized device sold for about $35 that plugs into home televisions and is used mainly to teach coding to children and promote computing in developing countries.