29 research outputs found
Tracking Cyber Adversaries with Adaptive Indicators of Compromise
A forensics investigation after a breach often uncovers network and host
indicators of compromise (IOCs) that can be deployed to sensors to allow early
detection of the adversary in the future. Over time, the adversary will change
tactics, techniques, and procedures (TTPs), which will also change the data
generated. If the IOCs are not kept up-to-date with the adversary's new TTPs,
the adversary will no longer be detected once all of the IOCs become invalid.
Tracking the Known (TTK) is the problem of keeping IOCs, in this case regular
expressions (regexes), up-to-date with a dynamic adversary. Our framework
solves the TTK problem in an automated, cyclic fashion to bracket a previously
discovered adversary. This tracking is accomplished through a data-driven
approach of self-adapting a given model based on its own detection
capabilities.
In our initial experiments, we found that the true positive rate (TPR) of the
adaptive solution degrades much less significantly over time than the naive
solution, suggesting that self-updating the model allows the continued
detection of positives (i.e., adversaries). The cost for this performance is in
the false positive rate (FPR), which increases over time for the adaptive
solution, but remains constant for the naive solution. However, the difference
in overall detection performance, as measured by the area under the curve
(AUC), between the two methods is negligible. This result suggests that
self-updating the model over time should be done in practice to continue to
detect known, evolving adversaries.Comment: This was presented at the 4th Annual Conf. on Computational Science &
Computational Intelligence (CSCI'17) held Dec 14-16, 2017 in Las Vegas,
Nevada, US
A Riemann solver at a junction compatible with a homogenization limit
We consider a junction regulated by a traffic lights, with n incoming roads
and only one outgoing road. On each road the Phase Transition traffic model,
proposed in [6], describes the evolution of car traffic. Such model is an
extension of the classic Lighthill-Whitham-Richards one, obtained by assuming
that different drivers may have different maximal speed. By sending to infinity
the number of cycles of the traffic lights, we obtain a justification of the
Riemann solver introduced in [9] and in particular of the rule for determining
the maximal speed in the outgoing road.Comment: 19 page
Understanding the Reactivity of Enol Ether Radical Cations: Investigation of Anodic Four-Membered Carbon Ring Formation
The reactivity of enol ether radical
cations was investigated in
anodic four-membered carbon ring formations, advancing the mechanistic
understanding of these reactions. The mono-ring-containing aromatic
cations were reduced through inter- or intramolecular electron transfer
to give mono- or bis-ring-containing compounds, respectively. Small
structural changes in the hydrocarbon linkers tethering two aromatic
rings exerted a powerful effect on the efficiency of such electron
transfer events
Hydrogen-Bonding-Induced Fluorescence: Water-Soluble and Polarity-Independent Solvatochromic Fluorophores
Fluorophores
with emission wavelengths that shift depending on
their hydrogen-bonding microenvironment in water would be fascinating
tools for the study of biological events. Herein we describe the design
and synthesis of a series of water-soluble solvatochromic fluorophores,
2,5-bisÂ(oligoethylene glycol)Âoxybenzaldehydes (<b>8</b>–<b>11</b>) and 2,5-bisÂ(oligoethylene glycol)Âoxy-1,4-dibenzaldehydes
(<b>14</b>–<b>17</b>), based on a push–pull
strategy. Unlike typical examples in this class of fluorophores, the
fluorescence properties of these compounds are independent of solvent
polarity and become fluorescent upon intermolecular hydrogen-bonding,
exhibiting high quantum yields (up to Ď• = 0.55) and large Stokes
shifts (up to 134 nm). Furthermore, their emission wavelengths change
depending on their hydrogen-bonding environment. The described fluorophores
provide a starting point for unprecedented applications in the fields
of chemical biology and medicinal chemistry
Soluble Tag-Assisted Peptide Head-to-Tail Cyclization: Total Synthesis of Mahafacyclin B
A soluble tag-assisted liquid-phase method was successfully applied to peptide head-to-tail cyclization, leading to the total synthesis of antimalarial cyclic heptapeptide, mahafacyclin B (<b>1</b>). The cyclization was carried out in the liquid phase with the tag remaining, which allowed rapid reaction workup and product isolation
Total Synthesis of Elastin Peptide Using High Pressure–Liquid Phase Synthesis Assisted by a Soluble Tag Strategy
A highly
aggregating elastin peptide was prepared efficiently using
a high pressure–liquid phase synthesis approach assisted by
a soluble tag strategy. Two standard syringes were connected to each
other to construct a reactor. This simple reactor was used to apply
high pressure to the highly viscous reaction mixture thereby maintaining
its fluidity. The reactions were completely inhibited due to aggregation
when conducted in a standard flask reactor, whereas our high pressure
approach accelerated the couplings to realize complete conversion
within 5–7 min. All steps were conducted at 0.10 M concentration,
affording grams of the desired product
Mahafcyclin B alters the morphology of CHO-K1 cells.
<p>Morphology was measured using continuous boxplots for eccentricity, major-axis length, and minor-axis length of each cell in response to mahafacyclin B.</p
Synthetic Method for Oligonucleotide Block by Using Alkyl-Chain-Soluble Support
A straightforward method for the
synthesis of oligonucleotide blocks
using a Cbz-type alkyl-chain-soluble support (Z-ACSS) attached to
the 3′-OH group of 3′-terminal nucleosides was developed.
The Z-ACSS allowed for the preparation of fully protected deoxyribo-
and ribo-oligonucleotides without chromatographic purification and
released dimer- to tetramer-size oligonucleotide blocks via hydrogenation
using a Pd/C catalyst without significant loss or migration of protective
groups such as 5′-end 4,4′-dimethoxtrityl, 2-cyanoethyl
on internucleotide bonds, or 2′-TBS
Mahafacyclin B alters the expression of a subset of genes in CHO-K1 cells.
<p>Genes marked in purple were detected as differentially expressed at the 5% false-discovery rate (FDR) using TCC. (A) Scatter plot of differentially expressed genes in response to 0 or 0.22 ÎĽM mahafacyclin B. (B) Scatter plot of differentially expressed genes in response to 0 or 22 ÎĽM mahafacyclin B.</p
Purity of synthesized mahafacyclin B.
<p>(A) UV–Visible spectrum of LC-MS analysis of the sample (0%–100% 0.1%TFA CH<sub>3</sub>CN in 45 min). Peak purity was calculated using the peak area percentage. RT = 33.12 min was characterized as mahafacyclin B (96.8%) and RT = 30.69 min was found to be the epimerized variant (0.82%), the existence of which was determined by mass chromatogram (<i>m/z</i> 803–810, data not shown). (B) Mass spectrometry of the main peak in the UV–Visible spectrum of the LC-MS analysis of mahafacyclin B. <i>m/z</i> 804.2249 was characterized as [M+H], and <i>m/z</i> 1608.4589 (<i>m/z</i> 1607.4438 for the monoisotopic ion) as [2M+H].</p