arXiv AI

Does Federated Training Degrade Explainability? A Comparative Analysis of Grad-CAM Faithfulness in Centralized vs. Federated Deepfake Detection

The paper investigates whether federated learning harms the faithfulness of Grad‑CAM explanations in deepfake detection. Using an EfficientNet‑B4 model on FaceForensics++ data distributed across five clients, the study finds that explanation quality is non‑monotonic: near‑IID and moderate heterogeneity yield explanations as good as or better than a centralized model, while extreme heterogeneity causes explanations to become spatially incoherent and causally misleading. The authors provide practical guidance for determining when federated deepfake detection can be safely deployed and when its explanations lose trustworthiness.

arXiv Machine Learning
Aug 20

FedLNS: Leverage LayerNorm Signature Modeling to Mitigate Adversarial Manipulation in Federated LLMs

FedLNS is a server‑side framework that screens federated learning updates by representing each client’s contribution through changes in trainable normalization‑layer parameters, creating lightweight signatures that can be compared against a history‑aware cross‑client reference. The method requires no extra client‑to‑server communication, raw data, or labeled attack examples, and after screening, the remaining full‑model updates are aggregated with standard federated learning rules. Experiments on GPT‑style, BERT‑style, and LLaMA‑style models with 200 clients demonstrate that FedLNS achieves lower test perplexity than six baselines even when 40% of the population performs target manipulation under both IID and non‑IID data partitions.

By Kai Li, Jong-Ik Park, Carlee Joe-Wong, Wei Ni, Falko Dressler
arXiv Machine Learning
Sep 23

FedNIA: Noise-Induced Activation Analysis for Mitigating Data Poisoning in Federated Learning

FedNIA is a defense framework for federated learning that identifies and excludes malicious clients without needing a central test dataset. It works by injecting random noise inputs and analyzing layerwise activation patterns with an autoencoder to detect abnormal behaviors caused by data poisoning. The method can counter various attack types—including sample poisoning, label flipping, and backdoors—even when multiple attackers collaborate, and shows strong performance on non‑iid federated datasets.

By Ehsan Hallaji, Roozbeh Razavi-Far, Mehrdad Saif
arXiv AI
Sep 24

Backdoors Leave Structural Traces: FedMAST for Backdoor Detection and Containment in Federated Learning

The paper introduces FedMAST, a Federated Multi‑Axis Structural Tracing defense designed to detect and contain backdoor attacks in federated learning. FedMAST evaluates client updates through complementary structural, spectral, and historical evidence, applying tiered filtering and round‑level containment. In experiments across six backdoor attacks, FedMAST consistently achieves lower attack success rates while preserving high main‑task accuracy.

By Srinivasan Subramanian, Kazi Aminul Islam, Md. Abdullah Al Hafiz Khan
arXiv Machine Learning
Oct 2

Compression Footprints as Security Signals for Model-Poisoning Defense in Federated Learning

The paper proposes using lossy compression as a security signal in federated learning by defining a "compression footprint"—a low‑dimensional set of statistics derived from the compressor’s output. It introduces CRAFT, a server‑side aggregation method that leverages these footprints to distinguish honest from malicious updates without extra client metadata or knowledge of attacker numbers. Experiments on six attacks and datasets show CRAFT often outperforms existing robust aggregation baselines, demonstrating that compression can simultaneously reduce communication and enhance security.

By Sachi Shome, William Eiers
arXiv AI
Aug 24

Explainable Deepfake Detection with Feature-robust Augmentation and Evidence-grounded Explanation Optimization

Explainable Deepfake Detection with Feature-robust Augmentation and Evidence-grounded Explanation Optimization proposes a new framework that improves deepfake detection and interpretability. The approach introduces Feature-robust Augmentation—diversified degradation-aware strategies combined with supervised contrastive learning and a mean-teacher architecture—to maintain accuracy on low-quality images. For explanations, it employs evidence-grounded preference optimization, guiding the model to focus on genuine manipulation traces by learning from chosen-rejected explanation pairs that omit evidence or inject irrelevant details. The method achieved first place in the ACM Multimedia 2026 Explainable Deepfake Detection Challenge and is publicly available on GitHub.

By Zhu Xu, Jiaqi Tang, Pokai Chen, Yuxin Peng, Yang Liu
arXiv Machine Learning
Oct 16

Federated Art Chase: Privacy Leakage and Data Poisoning in Federated Fine-Tuning

The paper investigates privacy and integrity risks in federated fine‑tuning of a pretrained MobileNetV4 model on Quick, Draw! data. It shows that a single client update can reveal private labels, that label‑count recovery degrades with more clients, and that backdoor and label‑flipping attacks can succeed under FedAvg but are mitigated by FLTrust. The study also demonstrates a live poisoning session using Indigma’s FedMaestro orchestrator.

By Vasileios Perifanis, Nikolaos Pavlidis
arXiv Machine Learning
Sep 7

Federated Attack Campaign Detection via Contrastive Encoding of Threat Indicators in Gradient Updates

The paper introduces FedIoC, a federated learning framework that embeds structured threat indicators into gradient updates using a supervised contrastive loss. By aligning gradients from clients that share indicators for the same attack campaign, the server can cluster updates via cosine similarity to recover global campaign patterns without transmitting sensitive indicators. Experiments on two public threat‑detection benchmarks show that the server successfully identifies cross‑organizational campaign cohorts from fragmented local data.

By Manuel R\"oder, Bibin Babu, Frank-Michael Schleif