  Despite that deep neural networks (DNNs) have achieved enormous success in
many domains like natural language processing (NLP), they have also been proven
to be vulnerable to maliciously generated adversarial examples. Such inherent
vulnerability has threatened various real-world deployed DNNs-based
applications. To strength the model robustness, several countermeasures have
been proposed in the English NLP domain and obtained satisfactory performance.
However, due to the unique language properties of Chinese, it is not trivial to
extend existing defenses to the Chinese domain. Therefore, we propose AdvGraph,
a novel defense which enhances the robustness of Chinese-based NLP models by
incorporating adversarial knowledge into the semantic representation of the
input. Extensive experiments on two real-world tasks show that AdvGraph
exhibits better performance compared with previous work: (i) effective - it
significantly strengthens the model robustness even under the adaptive attacks
setting without negative impact on model performance over legitimate input;
(ii) generic - its key component, i.e., the representation of connotative
adversarial knowledge is task-agnostic, which can be reused in any
Chinese-based NLP models without retraining; and (iii) efficient - it is a
light-weight defense with sub-linear computational complexity, which can
guarantee the efficiency required in practical scenarios.
