31,136 research outputs found
Modeling Epidemic Spread in Synthetic Populations - Virtual Plagues in Massively Multiplayer Online Games
A virtual plague is a process in which a behavior-affecting property spreads
among characters in a Massively Multiplayer Online Game (MMOG). The MMOG
individuals constitute a synthetic population, and the game can be seen as a
form of interactive executable model for studying disease spread, albeit of a
very special kind. To a game developer maintaining an MMOG, recognizing,
monitoring, and ultimately controlling a virtual plague is important,
regardless of how it was initiated. The prospect of using tools, methods and
theory from the field of epidemiology to do this seems natural and appealing.
We will address the feasibility of such a prospect, first by considering some
basic measures used in epidemiology, then by pointing out the differences
between real world epidemics and virtual plagues. We also suggest directions
for MMOG developer control through epidemiological modeling. Our aim is
understanding the properties of virtual plagues, rather than trying to
eliminate them or mitigate their effects, as would be in the case of real
infectious disease.Comment: Accepted for presentation at Digital Games Research Association
(DiGRA) conference in Tokyo in September 2007. All comments to the authors
(mail addresses are in the paper) are welcom
Epidemic Thresholds with External Agents
We study the effect of external infection sources on phase transitions in
epidemic processes. In particular, we consider an epidemic spreading on a
network via the SIS/SIR dynamics, which in addition is aided by external agents
- sources unconstrained by the graph, but possessing a limited infection rate
or virulence. Such a model captures many existing models of externally aided
epidemics, and finds use in many settings - epidemiology, marketing and
advertising, network robustness, etc. We provide a detailed characterization of
the impact of external agents on epidemic thresholds. In particular, for the
SIS model, we show that any external infection strategy with constant virulence
either fails to significantly affect the lifetime of an epidemic, or at best,
sustains the epidemic for a lifetime which is polynomial in the number of
nodes. On the other hand, a random external-infection strategy, with rate
increasing linearly in the number of infected nodes, succeeds under some
conditions to sustain an exponential epidemic lifetime. We obtain similar sharp
thresholds for the SIR model, and discuss the relevance of our results in a
variety of settings.Comment: 12 pages, 2 figures (to appear in INFOCOM 2014
Innovative in silico approaches to address avian flu using grid technology
The recent years have seen the emergence of diseases which have spread very
quickly all around the world either through human travels like SARS or animal
migration like avian flu. Among the biggest challenges raised by infectious
emerging diseases, one is related to the constant mutation of the viruses which
turns them into continuously moving targets for drug and vaccine discovery.
Another challenge is related to the early detection and surveillance of the
diseases as new cases can appear just anywhere due to the globalization of
exchanges and the circulation of people and animals around the earth, as
recently demonstrated by the avian flu epidemics. For 3 years now, a
collaboration of teams in Europe and Asia has been exploring some innovative in
silico approaches to better tackle avian flu taking advantage of the very large
computing resources available on international grid infrastructures. Grids were
used to study the impact of mutations on the effectiveness of existing drugs
against H5N1 and to find potentially new leads active on mutated strains. Grids
allow also the integration of distributed data in a completely secured way. The
paper presents how we are currently exploring how to integrate the existing
data sources towards a global surveillance network for molecular epidemiology.Comment: 7 pages, submitted to Infectious Disorders - Drug Target
Malware Detection Module using Machine Learning Algorithms to Assist in Centralized Security in Enterprise Networks
Malicious software is abundant in a world of innumerable computer users, who
are constantly faced with these threats from various sources like the internet,
local networks and portable drives. Malware is potentially low to high risk and
can cause systems to function incorrectly, steal data and even crash. Malware
may be executable or system library files in the form of viruses, worms,
Trojans, all aimed at breaching the security of the system and compromising
user privacy. Typically, anti-virus software is based on a signature definition
system which keeps updating from the internet and thus keeping track of known
viruses. While this may be sufficient for home-users, a security risk from a
new virus could threaten an entire enterprise network. This paper proposes a
new and more sophisticated antivirus engine that can not only scan files, but
also build knowledge and detect files as potential viruses. This is done by
extracting system API calls made by various normal and harmful executable, and
using machine learning algorithms to classify and hence, rank files on a scale
of security risk. While such a system is processor heavy, it is very effective
when used centrally to protect an enterprise network which maybe more prone to
such threats.Comment: 6 page
Strategic Investment in Protection in Networked Systems
We study the incentives that agents have to invest in costly protection
against cascading failures in networked systems. Applications include
vaccination, computer security and airport security. Agents are connected
through a network and can fail either intrinsically or as a result of the
failure of a subset of their neighbors. We characterize the equilibrium based
on an agent's failure probability and derive conditions under which equilibrium
strategies are monotone in degree (i.e. in how connected an agent is on the
network). We show that different kinds of applications (e.g. vaccination,
malware, airport/EU security) lead to very different equilibrium patterns of
investments in protection, with important welfare and risk implications. Our
equilibrium concept is flexible enough to allow for comparative statics in
terms of network properties and we show that it is also robust to the
introduction of global externalities (e.g. price feedback, congestion).Comment: 32 pages, 3 figure
The Behavior of Epidemics under Bounded Susceptibility
We investigate the sensitivity of epidemic behavior to a bounded
susceptibility constraint -- susceptible nodes are infected by their neighbors
via the regular SI/SIS dynamics, but subject to a cap on the infection rate.
Such a constraint is motivated by modern social networks, wherein messages are
broadcast to all neighbors, but attention spans are limited. Bounded
susceptibility also arises in distributed computing applications with download
bandwidth constraints, and in human epidemics under quarantine policies.
Network epidemics have been extensively studied in literature; prior work
characterizes the graph structures required to ensure fast spreading under the
SI dynamics, and long lifetime under the SIS dynamics. In particular, these
conditions turn out to be meaningful for two classes of networks of practical
relevance -- dense, uniform (i.e., clique-like) graphs, and sparse, structured
(i.e., star-like) graphs. We show that bounded susceptibility has a surprising
impact on epidemic behavior in these graph families. For the SI dynamics,
bounded susceptibility has no effect on star-like networks, but dramatically
alters the spreading time in clique-like networks. In contrast, for the SIS
dynamics, clique-like networks are unaffected, but star-like networks exhibit a
sharp change in extinction times under bounded susceptibility.
Our findings are useful for the design of disease-resistant networks and
infrastructure networks. More generally, they show that results for existing
epidemic models are sensitive to modeling assumptions in non-intuitive ways,
and suggest caution in directly using these as guidelines for real systems
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