malware can not bring down a plane's computers, it close to impossible to compromise the computer system on a plane and make it crash like this, simply because of the way they are setup.
Planes have an average of 5 computers on board, standard operations will have 3 active 1 backup and 1 offline, if at anytime there is a discrepancy between the computers, the two systems that collude will override the 1 system that doesn't, that 1 system is then forced into a diagnostic mode and or rebooted, if the system is unrecoverable then the backup system takes over it's place. Should 2 systems enter an unrecoverable state the computer systems enters a new configuration whereby 1 system acts as primary and the other as a secondary mirror which allows instantaneous transfer of controls from the primary to secondary should the primary become compromised.
The 5th system is also powered up the moment 2 systems become unrecoverable, this is a unique system, it is never connected to the 4 other system and remains unpowered until needed, this is to prevent cross contamination and also allows it be unaffected by EMP abnormalities, it is also a reduced functionality system where by everything but the bare essentials for flying and landing a plane has been removed (based upon the principle that any extra function is another thing that can go wrong)
Even then there is a final fail safe system that is activated should things look like it's all going south, the ram air turbine is deployed and the mechanical/electrical manual controls are activated allow the pilot to take direct control of the plane
unfortunately no amount of backups and safety feature will compensate for stupid operator errors......