Adversarial examples highlight model vulnerabilities and are useful for
evaluation and interpretation. We define universal adversarial triggers:
input-agnostic sequences of tokens that trigger a model to produce a specific
prediction when concatenated to any input from a dataset. We propose a
gradient-guided search over tokens which finds short trigger sequences (e.g.,
one word for classification and four words for language modeling) that
successfully trigger the target prediction. For example, triggers cause SNLI
entailment accuracy to drop from 89.94% to 0.55%, 72% of "why" questions in
SQuAD to be answered "to kill american people", and the GPT-2 language model to
spew racist output even when conditioned on non-racial contexts. Furthermore,
although the triggers are optimized using white-box access to a specific model,
they transfer to other models for all tasks we consider. Finally, since
triggers are input-agnostic, they provide an analysis of global model behavior.
For instance, they confirm that SNLI models exploit dataset biases and help to
diagnose heuristics learned by reading comprehension models.

本篇论文旨在寻找普适的对抗触发器 (universal adversarial triggers)，使用梯度导向的搜索过程寻找跨任务短小的触发序列，并展示了触发序列的强大攻击性能。触发序列即使在输入无关的情况下，对模型的全局行为也提供了一种分析方法。