Something becoming corrupted is plausible, a virus is not even a possibility.
As for the ECU being damaged, a tune is a software issue, thus should be fixable through software means (a reflash). If the ECU were actually physically damaged, the car would likely not function at all.
Also, with the throttle in this car being drive by wire, there could be some electrical issue with the throttle body.
As far as having steering/brake failure, that is also not possible. The brakes are a mechanical system, they do not need a computer or electricity to function, same with the steering, although it is electric power steering, the car is still capable of being steered with no electricity. I do both of these all the time when pulling into my driveway, put the car into neutral and shut the car off. The car is still capable of stopping and steering.
99 Chevrolet Camaro Z28 M6 - 6.676 @ 103 in 1/8, 10.512 @ 130.2 on street tires, H/C/I
93 Eagle Talon TSI AWD 5spd - Built 6 Bolt, 16G Evo3, HKS 272 Cams - under construction
94 Mustang GT - 5.0 bored and stroked to 347, Vortech V1 @ 10 PSI, Tremec TKO 600 - PIA