Countermeasures Against Backdoor Attacks Towards Malware Detectors

Attacks on machine learning systems have been systematized as adversarial machine learning, and a variety of attack algorithms have been studied until today. In the malware classification problem, several papers have suggested the possibility of real-world attacks against machine learning-based malware classification models. A data poisoning attack is an attack technique in which an attacker mixes poisoned data into the training data, and the model learns from the poisoned training data to cause misclassification of specific (or unspecified) data. Although various poisoning attacks that inject poison into the feature space of malware classification models have been proposed, Severi et al. proposed the first backdoor poisoning attack in the input space towards malware detectors by injecting poison into the actual binary files in the data accumulation phase. They achieved an attack success rate of more than 90% by adding only 1% of the poison data to approximately 2% of the entire features with a backdoor. To the best of our knowledge, no fundamental countermeasure against these attacks has been proposed. In this paper, we propose the first countermeasure based on autoencoders in a realistic threat model such that a defender is available for the contaminated training data only. We replaced all potentially attackable dimensions with surrogate data generated by autoencoders instead of using autoencoders as anomaly detectors. The results of our experiments show that we succeeded in significantly reducing the attack success rate while maintaining the high prediction accuracy of the clean data using replacement with the autoencoder. Our results suggest a new possibility of autoencoders as a countermeasure against poisoning attacks.