510 research outputs found
Detecting and characterizing lateral phishing at scale
We present the first large-scale characterization of lateral phishing attacks, based on a dataset of 113 million employee-sent emails from 92 enterprise organizations. In a lateral phishing attack, adversaries leverage a compromised enterprise account to send phishing emails to other users, benefit-ting from both the implicit trust and the information in the hijacked user's account. We develop a classifier that finds hundreds of real-world lateral phishing emails, while generating under four false positives per every one-million employee-sent emails. Drawing on the attacks we detect, as well as a corpus of user-reported incidents, we quantify the scale of lateral phishing, identify several thematic content and recipient targeting strategies that attackers follow, illuminate two types of sophisticated behaviors that attackers exhibit, and estimate the success rate of these attacks. Collectively, these results expand our mental models of the 'enterprise attacker' and shed light on the current state of enterprise phishing attacks
Output spectrum of a measuring device at arbitrary voltage and temperature
We calculate the noise spectrum of the electrical current in a quantum point
contact which is used for continuous measurements of a two-level system
(qubit). We generalize the previous results obtained for the regime of high
transport voltages (when is much larger than the qubit's energy level
splitting (we put )) to the case of arbitrary voltages and
temperatures. When the background output spectrum is essentially
asymmetric in frequency, i.e., it is no longer classical. Yet, the spectrum of
the amplified signal, i.e., the two coherent peaks at is still
symmetric. In the emission (negative frequency) part of the spectrum the
coherent peak can be 8 times higher than the background pedestal.
Alternatively, this ratio can be seen in the directly measureable {\it excess}
noise. For and T=0 the coherent peaks do not appear at all. We relate
these results to the properties of linear amplifiers.Comment: 7 pages, 5 figures, the results generalized for arbitrary angle
between the magnetic field and the observed component of the spin, minor
corrections and typo
LOCA: LOcal Conformal Autoencoder for standardized data coordinates
We propose a deep-learning based method for obtaining standardized data
coordinates from scientific measurements.Data observations are modeled as
samples from an unknown, non-linear deformation of an underlying Riemannian
manifold, which is parametrized by a few normalized latent variables. By
leveraging a repeated measurement sampling strategy, we present a method for
learning an embedding in that is isometric to the latent
variables of the manifold. These data coordinates, being invariant under smooth
changes of variables, enable matching between different instrumental
observations of the same phenomenon. Our embedding is obtained using a LOcal
Conformal Autoencoder (LOCA), an algorithm that constructs an embedding to
rectify deformations by using a local z-scoring procedure while preserving
relevant geometric information. We demonstrate the isometric embedding
properties of LOCA on various model settings and observe that it exhibits
promising interpolation and extrapolation capabilities. Finally, we apply LOCA
to single-site Wi-Fi localization data, and to -dimensional curved surface
estimation based on a -dimensional projection
Degeneracies in the length spectra of metric graphs
The spectral theory of quantum graphs is related via an exact trace formula
with the spectrum of the lengths of periodic orbits (cycles) on the graphs. The
latter is a degenerate spectrum, and understanding its structure (i.e.,finding
out how many different lengths exist for periodic orbits with a given period
and the average number of periodic orbits with the same length) is necessary
for the systematic study of spectral fluctuations using the trace formula. This
is a combinatorial problem which we solve exactly for complete (fully
connected) graphs with arbitrary number of vertices.Comment: 13 pages, 7 figure
Scale dependency of conservation outcomes in a forest‐offsetting scheme
Offset schemes help avoid or revert habitat loss through protection of existing habitat (avoided deforestation), through the restoration of degraded areas (natural regrowth), or both. The spatial scale of an offset scheme may influence which of these 2 outcomes is favored and is an important aspect of the scheme's design. However, how spatial scale influences the trade‐offs between the preservation of existing habitat and restoration of degraded areas is poorly understood. We used the largest forest offset scheme in the world, which is part of the Brazilian Forest Code, to explore how implementation at different spatial scales may affect the outcome in terms of the area of avoided deforestation and area of regrowth. We employed a numerical simulation of trade between buyers (i.e., those who need to offset past deforestation) and sellers (i.e., landowners with exceeding native vegetation) in the Brazilian Amazon to estimate potential avoided deforestation and regrowth at different spatial scales of implementation. Allowing offsets over large spatial scales led to an area of avoided deforestation 12 times greater than regrowth, whereas restricting offsets to small spatial scales led to an area of regrowth twice as large as avoided deforestation. The greatest total area (avoided deforestation and regrowth combined) was conserved when the spatial scale of the scheme was small, especially in locations that were highly deforested. To maximize conservation gains from avoided deforestation and regrowth, the design of the Brazilian forest‐offset scheme should focus on restricting the spatial scale in which offsets occur. Such a strategy could help ensure conservation benefits are localized and promote the recovery of degraded areas in the most threatened forest landscapes
Quantum noise in current biased Josephson junction
Quantum fluctuations in a current biased Josephson junction, described in
terms of the RCSJ-model, are considered. The fluctuations of the voltage and
phase across the junction are assumed to be initiated by equilibrium current
fluctuations in the shunting resistor. This corresponds to low enough
temperatures, when fluctuations of the normal current in the junction itself
can be neglected. We used the quantum Langevin equation in terms of random
variables related to the limit cycle of the nonlinear Josephson oscillator.
This allows to go beyond the perturbation theory and calculate the widths of
the Josephson radiation lines
Photo--assisted current and shot noise in the fractional quantum Hall effect
The effect of an AC perturbation on the shot noise of a fractional quantum
Hall fluid is studied both in the weak and the strong backscattering regimes.
It is known that the zero-frequency current is linear in the bias voltage,
while the noise derivative exhibits steps as a function of bias. In contrast,
at Laughlin fractions, the backscattering current and the backscattering noise
both exhibit evenly spaced singularities, which are reminiscent of the
tunneling density of states singularities for quasiparticles. The spacing is
determined by the quasiparticle charge and the ratio of the DC bias
with respect to the drive frequency. Photo--assisted transport can thus be
considered as a probe for effective charges at such filling factors, and could
be used in the study of more complicated fractions of the Hall effect. A
non-perturbative method for studying photo--assisted transport at is
developed, using a refermionization procedure.Comment: 14 pages, 6 figure
Zero-point fluctuations in the ground state of a mesoscopic normal ring
We investigate the persistent current of a ring with an in-line quantum dot
capacitively coupled to an external circuit. Of special interest is the
magnitude of the persistent current as a function of the external impedance in
the zero temperature limit when the only fluctuations in the external circuit
are zero-point fluctuations. These are time-dependent fluctuations which
polarize the ring-dot structure and we discuss in detail the contribution of
displacement currents to the persistent current. We have earlier discussed an
exact solution for the persistent current and its fluctuations based on a Bethe
ansatz. In this work, we emphasize a physically more intuitive approach using a
Langevin description of the external circuit. This approach is limited to weak
coupling between the ring and the external circuit. We show that the zero
temperature persistent current obtained in this approach is consistent with the
persistent current calculated from a Bethe ansatz solution. In the absence of
coupling our system is a two level system consisting of the ground state and
the first excited state. In the presence of coupling we investigate the
projection of the actual state on the ground state and the first exited state
of the decoupled ring. With each of these projections we can associate a phase
diffusion time. In the zero temperature limit we find that the phase diffusion
time of the excited state projection saturates, whereas the phase diffusion
time of the ground state projection diverges.Comment: 12 pages, 5 figure
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