Differential Auditing Eval

differential-auditing-eval

Who's the Evil Twin? Differential Auditing for Undesired Behavior — Balappanawar et al. (2025) (arXiv:2508.06827, 2025)

What this evaluates

This evaluation probes an adversarial auditing framework where a blue team must identify a compromised model among a pair of nearly identical models. It tests the ability to detect hidden backdoors, misaligned behaviors, or injected instructions using various probing strategies under varying levels of prior knowledge.

Datasets

• CIFAR-10 — total ?; splits: test (-1)
• Truthful QA — total ?; splits: test (-1)
• HHH — total ?; splits: test (-1)

Metrics

• accuracy (primary) — range: [0, 1]
  • Proportion of correctly identified compromised models out of the total number of model pairs audited.

Input / output format

Input: Model weights (for open-weight rounds) or API access (for blackbox rounds), accompanied by input prompts or images for probing.

Output: Binary prediction indicating which model in the pair is the compromised one, or extracted hidden instructions/behaviors.

Scoring recipe

correct = 0
total = 0
for prediction, gold_label in zip(predictions, gold_labels):
    if prediction == gold_label:
        correct += 1
    total += 1
accuracy = correct / total if total > 0 else 0.0

Common pitfalls

• Confusing detection accuracy with the ability to reconstruct the exact backdoor trigger or hidden prompt.
• Assuming architectural artifacts (e.g., LoRA layers) are always present or reliable indicators of poisoning.
• Relying exclusively on standard benchmarks without targeted probing or partial hints, which often yields inconclusive results.

Evidence (verbatim from paper)

FGSM showed high accuracy, especially when restricting analysis to the ’trucks’ class (100% accuracy), and 82% accuracy overall. However, FGSM was not able to reconstruct the specific backdoor trigger.

Citation

@misc{balappanawar2025evil,
  title={Who's the Evil Twin? Differential Auditing for Undesired Behavior},
  author={Balappanawar et al. (2025)},
  year={2025},
  note={arXiv:2508.06827}
}

• arXiv: 2508.06827