I use to do work for the US Navy at our lab and network security was an extremely important consideration. The tactical systems needed an air-gap between the weapon systems and any other system with some form of external communications. Even entry ports for remote maintenance were of great concern because the satellites used for that session might be breached by a foreign adversary who could then enter the the ships infrastructure. Keeping all these cell phones and other equipment completely separated is more difficult than it sounds, so regular security scanning an monitoring for alternate pathways between various system is extremely important to look for. All you need is one bad actor to plugin some device to the local network and all the security goes out the window. Prevention of any rogue connections between networks must be monitored and enforced.
There must also be a way to terminate all external "general" communications that is not mission critical on a moments notice. All mission critical traffic must be characterized and alarms go off when undocumented traffic is seen. Not doing all of this is only going to entice the Russians and Chinese to infiltrate the systems waiting for their moment to disrupt everything. If they are smart, you won't know until they throw the switch.
Having so many devices on board makes it all that much easier for the adversary. One cell phone running a rogue app on it might be all it takes. Remember, each cell phone has GPS and knows exactly where the ship is, where the Chinese/Russians wish there was a big hole in the water instead. Every single cell phone must therefor be monitored to ensure that GPS is disabled while out at sea. Devices that are not properly configured for mission security will definitely sink ships.