[X] Have Reizay, a trained security operative take charge of the investigation, not withstanding the fact her training is from the Closed Dyson. It's unlikely to make her - or you - popular but she will find something.
[X] Work with Reizay and Lanaiatte to try to determine when the software weapon was introduced to the submarine to try to narrow down the suspect list. It'll take time but minimise disruption to the mission or the crew until you can act more surgically.
[X] Given both the Communion and the Chrysanthemum have had infiltration, there's no way to localise things easily. It's best to just interview everyone and use the combination of expertise in the group to figure out who's a problem. It'll be more intrusive than just checking the software but if it works it could nail a suspect.
