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Federated Graph Anomaly Detection Through Contrastive Learning with Global Negative Pairs
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Proposes FedCLGN, a federated graph anomaly detection framework that maintains a server-side pool of global negative pairs (embeddings of pseudo-labeled anomalous nodes uploaded by clients), diffuses them with personalized PageRank, and uses CoLA-style contrastive learning with FedPub-style personalized aggregation.
Problem
Anomaly detection on attributed graphs distributed across clients in federated settings, where restricted data access and missing cross-client edges make contrastive negative-pair sampling less effective and centralized methods degrade.
Approach
Clients pseudo-label anomalous nodes and upload only the negative-pair embeddings of those nodes; the server aggregates them into a global negative pair pool, refines it with personalized PageRank diffusion, and redistributes it to clients to strengthen contrastive positive/negative discrimination, combined with personalized aggregation weighted by negative-pair similarity.
Key results
- FedCLGN achieves the best AUC on all four datasets, e.g., 0.861 on Cora with 5 clients vs 0.806 for the best federated baseline (FedPub-CoLA).
- On Flickr with 5 clients FedCLGN reaches 0.876 AUC vs 0.759 for CoLA and 0.756 for FedAvg-CoLA.
- Parameter study suggests confidence threshold lambda in [-0.3, -0.5] works best, and transfer probability alpha gives stable performance across 0.1-0.9.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use FedCLGN instead of the strongest reported baseline | Federated graph anomaly detection · Cora, 5/10/15 clients | AUC: 0.806±0.011 -> 0.861±0.009; 0.796±0.015 -> 0.807±0.010; 0.789±0.011 -> 0.800±0.002 | Helped |
| Use FedCLGN instead of the strongest reported baseline | Federated graph anomaly detection · Citeseer, 5/10/15 clients | AUC: 0.814±0.014 -> 0.840±0.008; 0.814±0.013 -> 0.826±0.008; 0.738±0.003 -> 0.812±0.007 | Helped |
| Use FedCLGN instead of the strongest reported baseline | Federated graph anomaly detection · BlogCatalog, 5/10/15 clients | AUC: 0.825±0.012 -> 0.846±0.004; 0.800±0.008 -> 0.823±0.005; 0.805±0.007 -> 0.840±0.004 | Helped |
| Use FedCLGN instead of the strongest reported baseline | Federated graph anomaly detection · Flickr, 5/10/15 clients | AUC: 0.775±0.006 -> 0.876±0.001; 0.758±0.005 -> 0.858±0.002; 0.806±0.002 -> 0.849±0.009 | Helped |
| Add pseudo-label discovery and global negative-pair diffusion (ablation) | FedPub-CoLA / FedCLGN · Cora, 5/10/15 clients | AUC: 0.806±0.011 -> 0.861±0.009; 0.751±0.009 -> 0.807±0.010; 0.655±0.021 -> 0.800±0.002 | Helped |
| Add pseudo-label discovery and global negative-pair diffusion (ablation) | FedPub-CoLA / FedCLGN · Citeseer, 5/10/15 clients | AUC: 0.796±0.011 -> 0.840±0.008; 0.795±0.003 -> 0.826±0.008; 0.712±0.005 -> 0.812±0.007 | Helped |
| Add pseudo-label discovery and global negative-pair diffusion (ablation) | FedPub-CoLA / FedCLGN · BlogCatalog, 5/10/15 clients | AUC: 0.823±0.004 -> 0.846±0.004; 0.793±0.008 -> 0.823±0.005; 0.805±0.007 -> 0.840±0.004 | Helped |
| Add pseudo-label discovery and global negative-pair diffusion (ablation) | FedPub-CoLA / FedCLGN · Flickr, 5/10/15 clients | AUC: 0.775±0.006 -> 0.876±0.001; 0.722±0.015 -> 0.858±0.002; 0.683±0.017 -> 0.849±0.009 | Helped |
Surprising findings
- Several federated CoLA variants degrade substantially as the number of clients grows from 5 to 15 (e.g., CoLA on Cora drops from 0.728 to 0.625), and FedAvg/FedPub variants fall below DOMINANT/MGAD at 15 clients on Cora.
Limitations
- Anomalies are synthetically injected rather than real ground-truth anomalies
- Performance of several federated variants degrades with more clients and FedCLGN also drops at 15 clients on some datasets
- Uses pseudo-labels with a confidence threshold, so errors in pseudo-labeling may propagate into the negative pool
Experimental setup
Datasets: Cora Citeseer BlogCatalog Flickr
Benchmarks: Cora Citeseer BlogCatalog Flickr
Metrics: ROC-AUC
Baselines: DOMINANT AnomalyDAE MGAD CoLA FedAvg-CoLA FedPub-CoLA
Builds on: CoLA FedPub FedAvg personalized PageRank
Closest papers by meaning
- UniFORM: Towards Unified Framework for Anomaly Detection on Graphs (AAAI 2025 · similarity 0.88)
- Federated Graph Learning under Domain Shift with Generalizable Prototypes (AAAI 2024 · similarity 0.87)
- Decoupled Subgraph Federated Learning (ICLR 2025 · similarity 0.87)
- Revisiting Graph Contrastive Learning on Anomaly Detection: A Structural Imbalance Perspective (AAAI 2025 · similarity 0.86)
- ARC: A Generalist Graph Anomaly Detector with In-Context Learning (NeurIPS 2024 · similarity 0.85)
- Graph Anomaly Detection as Dynamical Transport: Training-Free Scoring via Empirical Bayes (NeurIPS 2026 · similarity 0.85)
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