The Japan Aerospace Exploration Agency (JAXA) disclosed April 23 that an unauthorized outsider breached its network security to gain access to information about the international space station’s Kibo experiment module.

In a statement, JAXA said that the breach occurred April 17 in the middle of the night and was discovered April 18, at which time the server was disconnected from the network.

The intruder accessed mailing lists for Kibo operations personnel and reference information related to Kibo operation preparations, JAXA said.

“The information accessed at this time was not directly linked to the Kibo’s operation, thus we have confirmed that the incident has not affected operations,” JAXA said.

The agency said that it still is investigating the cause and impact of the unauthorized access and vowed to strengthen its information security to avoid a repeat.