What are backdoor (trojan) attacks on ML models, and how do you detect a poisoned model?
A backdoored model acts perfectly until it meets a secret trigger, then flips. The signal is explaining why clean test accuracy never exposes it, and what detection actually buys you when the trigger is unknown.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
A backdoored model acts perfectly until it meets a secret trigger, then flips. The signal is explaining why clean test accuracy never exposes it, and what detection actually buys you when the trigger is unknown.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
