Cost-effective outbreak detection in networks
Jure LeskovecAndreas KrauseCarlos GuestrinChristos FaloutsosJeanne VanBriesenNatalie Glance
Proposes the CELF algorithm for network outbreak detection, exploiting submodularity to place sensors up to 700 times faster than standard greedy methods while providing provable approximation guarantees on massive water and information networks.
The article addresses the challenge of efficiently detecting outbreaks or information cascades in large networks, such as placing sensors in water distribution systems to catch contaminants or selecting blogs to monitor for emerging stories. These tasks matter because monitoring every location or source is prohibitively expensive, yet delayed detection can lead to widespread harm or missed information, and simple intuitive strategies like choosing the largest nodes often perform poorly.
The article set out to develop a general methodology for selecting a budgeted set of nodes that detects such spreading processes as effectively as possible. It demonstrates that common detection objectives exhibit submodularity, a diminishing-returns property that enables efficient optimization with performance guarantees.
The work models the problem as maximizing a nondecreasing submodular reward function subject to a cost budget, then exploits this structure with the CELF algorithm, which combines lazy evaluations and cost-benefit comparisons. The approach was tested on an EPA water network model with millions of contamination scenarios and on a real blog dataset containing 10.5 million posts and 17,000 cascades.
Key findings show that CELF produces placements guaranteed to achieve at least half of (1-1/e) of the optimal reward, even with varying node costs, while running up to 700 times faster than a basic greedy method. Online bounds derived in the article prove solutions lie within roughly 5-15 percent of optimality in the evaluated cases. The algorithm substantially outperforms heuristics based on popularity or degree, and it reveals that cost-aware selection favors smaller, high-quality sources over large ones; multicriterion trade-offs can be explored by weighting objectives without losing submodularity.
These results matter because they turn an intractable combinatorial task into a practical, provably good procedure that reduces detection time, affected population, and monitoring cost across domains. Decision makers can therefore allocate limited sensors or reading time with quantified confidence rather than relying on intuition.
The article recommends applying the same submodular framework to related problems such as network security and immunization. When strong guarantees are needed before deployment, further simulation or pilot data on the specific network would strengthen . Main limitations include reliance on accurate cascade or contamination models and the assumption that outbreaks remain sparse; results may degrade if these conditions do not hold.
- Paper: Maximizing the spread of influence through a social network, David Kempe et al. (2003). This paper establishes the submodular optimization framework and greedy approximation guarantees for influence diffusion processes on networks that form the theoretical foundation of the source work.
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- Paper: Catastrophic cascade of failures in interdependent networks, S. Havlin et al. (2009). This work investigates cascading failure dynamics across coupled networks, extending single-network spreading models to interdependent infrastructures.
