As with other modules, various versions ala 1A/2E etc, each with an appropriately strong (or weak) chance of blocking the scan and/or alerting the authorities about the blocker. That would be SO way useful.
Perhaps it could be a special kind of cargo module designed for smuggling. So you could smuggle in that one and carry legal cargo in the other. The scanning ship would see the legal cargo but nothing in the special smuggling cargo module. It could only be bought via black market or anarchy/pirate systems, and several orders of magnitude more expensive than standard cargo modules.
They could also be illegal or legal depending on the system. Better ones have virtually no chance of the authorities noticing it. Getting caught could be a fine and confiscation of the module. Plus, of course, the fines for any illegally smuggled goods. It's fine to carry legal cargo, but you still get fined for having the module and it gets confiscated.
Perhaps it could be a special kind of cargo module designed for smuggling. So you could smuggle in that one and carry legal cargo in the other. The scanning ship would see the legal cargo but nothing in the special smuggling cargo module. It could only be bought via black market or anarchy/pirate systems, and several orders of magnitude more expensive than standard cargo modules.
They could also be illegal or legal depending on the system. Better ones have virtually no chance of the authorities noticing it. Getting caught could be a fine and confiscation of the module. Plus, of course, the fines for any illegally smuggled goods. It's fine to carry legal cargo, but you still get fined for having the module and it gets confiscated.