9,255 research outputs found
The Effect of Security Education and Expertise on Security Assessments: the Case of Software Vulnerabilities
In spite of the growing importance of software security and the industry
demand for more cyber security expertise in the workforce, the effect of
security education and experience on the ability to assess complex software
security problems has only been recently investigated. As proxy for the full
range of software security skills, we considered the problem of assessing the
severity of software vulnerabilities by means of a structured analysis
methodology widely used in industry (i.e. the Common Vulnerability Scoring
System (\CVSS) v3), and designed a study to compare how accurately individuals
with background in information technology but different professional experience
and education in cyber security are able to assess the severity of software
vulnerabilities. Our results provide some structural insights into the complex
relationship between education or experience of assessors and the quality of
their assessments. In particular we find that individual characteristics matter
more than professional experience or formal education; apparently it is the
\emph{combination} of skills that one owns (including the actual knowledge of
the system under study), rather than the specialization or the years of
experience, to influence more the assessment quality. Similarly, we find that
the overall advantage given by professional expertise significantly depends on
the composition of the individual security skills as well as on the available
information.Comment: Presented at the Workshop on the Economics of Information Security
(WEIS 2018), Innsbruck, Austria, June 201
An Effective Meaningful Way to Evaluate Survival Models
One straightforward metric to evaluate a survival prediction model is based
on the Mean Absolute Error (MAE) -- the average of the absolute difference
between the time predicted by the model and the true event time, over all
subjects. Unfortunately, this is challenging because, in practice, the test set
includes (right) censored individuals, meaning we do not know when a censored
individual actually experienced the event. In this paper, we explore various
metrics to estimate MAE for survival datasets that include (many) censored
individuals. Moreover, we introduce a novel and effective approach for
generating realistic semi-synthetic survival datasets to facilitate the
evaluation of metrics. Our findings, based on the analysis of the
semi-synthetic datasets, reveal that our proposed metric (MAE using
pseudo-observations) is able to rank models accurately based on their
performance, and often closely matches the true MAE -- in particular, is better
than several alternative methods.Comment: Accepted to ICML 202
Scalable Population Synthesis with Deep Generative Modeling
Population synthesis is concerned with the generation of synthetic yet
realistic representations of populations. It is a fundamental problem in the
modeling of transport where the synthetic populations of micro-agents represent
a key input to most agent-based models. In this paper, a new methodological
framework for how to 'grow' pools of micro-agents is presented. The model
framework adopts a deep generative modeling approach from machine learning
based on a Variational Autoencoder (VAE). Compared to the previous population
synthesis approaches, including Iterative Proportional Fitting (IPF), Gibbs
sampling and traditional generative models such as Bayesian Networks or Hidden
Markov Models, the proposed method allows fitting the full joint distribution
for high dimensions. The proposed methodology is compared with a conventional
Gibbs sampler and a Bayesian Network by using a large-scale Danish trip diary.
It is shown that, while these two methods outperform the VAE in the
low-dimensional case, they both suffer from scalability issues when the number
of modeled attributes increases. It is also shown that the Gibbs sampler
essentially replicates the agents from the original sample when the required
conditional distributions are estimated as frequency tables. In contrast, the
VAE allows addressing the problem of sampling zeros by generating agents that
are virtually different from those in the original data but have similar
statistical properties. The presented approach can support agent-based modeling
at all levels by enabling richer synthetic populations with smaller zones and
more detailed individual characteristics.Comment: 27 pages, 15 figures, 4 table
Climate change may have minor impact on zooplankton functional diversity in the Mediterranean Sea
Aim
To assess the impact of climate change on the functional diversity of marine zooplankton communities.
Location
The Mediterranean Sea.
Methods
We used the functional traits and geographic distributions of 106 copepod species to estimate the zooplankton functional diversity of Mediterranean surface assemblages for the 1965â1994 and 2069â2098 periods. Multiple environmental niche models were trained at the global scale to project the species habitat suitability in the Mediterranean Sea and assess their sensitivity to climate change predicted by several scenarios. Simultaneously, the species traits were used to compute a functional dendrogram from which we identified seven functional groups and estimated functional diversity through Faith's index. We compared the measured functional diversity to the one originated from null models to test if changes in functional diversity were solely driven by changes in species richness.
Results
All but three of the 106 species presented range contractions of varying intensity. A relatively low decrease of species richness (â7.42 on average) is predicted for 97% of the basin, with higher losses in the eastern regions. Relative sensitivity to climate change is not clustered in functional space and does not significantly vary across the seven copepod functional groups defined. Changes in functional diversity follow the same pattern and are not different from those that can be expected from changes in richness alone.
Main conclusions
Climate change is not expected to alter copepod functional traits distribution in the Mediterranean Sea, as the most and the least sensitive species are functionally redundant. Such redundancy should buffer the loss of ecosystem functions in Mediterranean zooplankton assemblages induced by climate change. Because the most negatively impacted species are affiliated to temperate regimes and share Atlantic biogeographic origins, our results are in line with the hypothesis of increasingly more tropical Mediterranean communities
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