2,384 research outputs found
HYPA: Efficient Detection of Path Anomalies in Time Series Data on Networks
The unsupervised detection of anomalies in time series data has important
applications in user behavioral modeling, fraud detection, and cybersecurity.
Anomaly detection has, in fact, been extensively studied in categorical
sequences. However, we often have access to time series data that represent
paths through networks. Examples include transaction sequences in financial
networks, click streams of users in networks of cross-referenced documents, or
travel itineraries in transportation networks. To reliably detect anomalies, we
must account for the fact that such data contain a large number of independent
observations of paths constrained by a graph topology. Moreover, the
heterogeneity of real systems rules out frequency-based anomaly detection
techniques, which do not account for highly skewed edge and degree statistics.
To address this problem, we introduce HYPA, a novel framework for the
unsupervised detection of anomalies in large corpora of variable-length
temporal paths in a graph. HYPA provides an efficient analytical method to
detect paths with anomalous frequencies that result from nodes being traversed
in unexpected chronological order.Comment: 11 pages with 8 figures and supplementary material. To appear at SIAM
Data Mining (SDM 2020
Multimodal Classification of Urban Micro-Events
In this paper we seek methods to effectively detect urban micro-events. Urban
micro-events are events which occur in cities, have limited geographical
coverage and typically affect only a small group of citizens. Because of their
scale these are difficult to identify in most data sources. However, by using
citizen sensing to gather data, detecting them becomes feasible. The data
gathered by citizen sensing is often multimodal and, as a consequence, the
information required to detect urban micro-events is distributed over multiple
modalities. This makes it essential to have a classifier capable of combining
them. In this paper we explore several methods of creating such a classifier,
including early, late, hybrid fusion and representation learning using
multimodal graphs. We evaluate performance on a real world dataset obtained
from a live citizen reporting system. We show that a multimodal approach yields
higher performance than unimodal alternatives. Furthermore, we demonstrate that
our hybrid combination of early and late fusion with multimodal embeddings
performs best in classification of urban micro-events
Robust modeling of human contact networks across different scales and proximity-sensing techniques
The problem of mapping human close-range proximity networks has been tackled
using a variety of technical approaches. Wearable electronic devices, in
particular, have proven to be particularly successful in a variety of settings
relevant for research in social science, complex networks and infectious
diseases dynamics. Each device and technology used for proximity sensing (e.g.,
RFIDs, Bluetooth, low-power radio or infrared communication, etc.) comes with
specific biases on the close-range relations it records. Hence it is important
to assess which statistical features of the empirical proximity networks are
robust across different measurement techniques, and which modeling frameworks
generalize well across empirical data. Here we compare time-resolved proximity
networks recorded in different experimental settings and show that some
important statistical features are robust across all settings considered. The
observed universality calls for a simplified modeling approach. We show that
one such simple model is indeed able to reproduce the main statistical
distributions characterizing the empirical temporal networks
A Survey of Graph-based Deep Learning for Anomaly Detection in Distributed Systems
Anomaly detection is a crucial task in complex distributed systems. A
thorough understanding of the requirements and challenges of anomaly detection
is pivotal to the security of such systems, especially for real-world
deployment. While there are many works and application domains that deal with
this problem, few have attempted to provide an in-depth look at such systems.
In this survey, we explore the potentials of graph-based algorithms to identify
anomalies in distributed systems. These systems can be heterogeneous or
homogeneous, which can result in distinct requirements. One of our objectives
is to provide an in-depth look at graph-based approaches to conceptually
analyze their capability to handle real-world challenges such as heterogeneity
and dynamic structure. This study gives an overview of the State-of-the-Art
(SotA) research articles in the field and compare and contrast their
characteristics. To facilitate a more comprehensive understanding, we present
three systems with varying abstractions as use cases. We examine the specific
challenges involved in anomaly detection within such systems. Subsequently, we
elucidate the efficacy of graphs in such systems and explicate their
advantages. We then delve into the SotA methods and highlight their strength
and weaknesses, pointing out the areas for possible improvements and future
works.Comment: The first two authors (A. Danesh Pazho and G. Alinezhad Noghre) have
equal contribution. The article is accepted by IEEE Transactions on Knowledge
and Data Engineerin
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