They can’t be hacked. They are fully autonomous androids. Trying to hack them is like someone trying to hack the calculators sitting on peoples desks.
An individual unit could possibly be tampered with, but the triple redundant independent sub-processor control system would detect the tampering and permanently destroy the unit. The same happens if the unit strays outside the Asimov rules.
And once again, you missed the point of the story line and focused on an irrelevant detail. :poke: