ReplaceDGA: BiLSTM-Based Adversarial DGA With High Anti-Detection Ability

Botnets extensively leverage Domain Generation Algorithms (DGAs) to establish reliable communication channels between bots and Command and Control (C&C) servers. Numerous character-level DGA classifiers have been extensively studied to detect and classify domain names generated by DGAs. Meanwhile, a series of adversarial domain generation algorithms have been proposed to evade DGA classifiers. Although the existing domain name generation algorithms have progressed against DGA classifier, their anti-detection abilities are still weak. This paper proposes a Bidirectional Long Short-Term Memory (BiLSTM) network-based adversarial DGA with high anti-detection ability, referred to as ReplaceDGA. ReplaceDGA requires no knowledge of the targeted DGA classifiers. It first builds a prediction model for benign domain names using the BiLSTM network to model the semantic relationship hidden within benign domain names and then replaces two characters of each input benign domain name based on the prediction model to maximize the similarity between the benign and generated domain names. Our experimental results validate that ReplaceDGA successfully evades various character-level DGA classifiers even after they are retrained by domain names generated by ReplaceDGA and outperforms the state-of-the-art adversarial DGAs in anti-detection ability, repetition rate, and collision rate. Our study of ReplaceDGA promotes the urgent need for developing more comprehensive and robust DGA classifiers that consider other factors besides character-level information of domain names.