Secure Federated Training: Detecting Compromised Nodes and Identifying the Type of Attacks

Abstract

Federated learning (FL) allows a set of clients to collaboratively train a model without sharing private data. As a result, FL has limited control over the local data and corresponding training process. Therefore, it is susceptible to poisoning attacks in which malicious clients use malicious training data or local updates to poison the global model. In this work, we first studied the data level and model level poisoning attacks. We simulated model poisoning attacks by tampering the local model updates during each round of communication and data poisoning attacks by training a few clients on malicious data. And clients under such attacks carry faulty information to the server, poison the global model, and restrict it from convergence. Therefore, detecting clients under attacks as well as identifying the type of attacks are required to recover the clients from their malicious status. To address these issues, we proposed a way under federated framework that enables the detection of malicious clients and attack types while ensuring data privacy. Our clustering-based approach utilizes the neuron’s activations from the local models to identify the type of poisoning attacks. We also proposed to check the weight distribution of local model updates among the participating clients to detect malicious clients. Our experimental results validated the robustness of the proposed framework against the attacks mentioned above by successfully detecting the compromised clients and the attack types. Moreover, the global model trained on MNIST data couldn’t reach the optimal point even after 75 rounds because of malicious clients, whereas the proposed approach by detecting the malicious clients ensured convergence within only 30 rounds and 40 rounds in independent and identically distributed (IID) and non- independent and identically distributed (non-IID) setup respectively.