The risk of a crash or collision suddenly becomes very real. It is not good enough to have a backup system that cannot be operated for fear it might become corrupted by the same virus that has hit the frontline operating system. Safe flying demands that the backup system is discrete and capable of taking over the full load of flight information instantly.
If you hand over the information then you’re sending the same virus through, aren’t you? And if you have a duplicate system that you’ve fed, in parallel, with the same information in real time then it’s got the virus too, right?