Before revision:  In this paper, we systematically study the backdoor attack against models on text data. First, we define the backdoor attack on text data. Then, we propose the different attack  strategies to generate trigger on text data . Next, we propose different types of the triggers based on modification scope, human recognition  and special cases.
After revision:  In this paper, we first propose the strategies to generate trigger on text data . Next, we propose different types of the triggers based on modification scope, human recognition and special cases.