Security Information and Event Management (SIEM) systems are today a key component of complex ent... more Security Information and Event Management (SIEM) systems are today a key component of complex enter-prise networks. They usually aggregate and correlate events from different machines and perform a rule-based analysis to detect threats. In this paper we present an enhancement of such systems which makes use of unsupervised anomaly detection algorithms without the need for any prior training of the system. For data acquisition, events are exported from an existing SIEM appliance, parsed, unified and preprocessed to fit the requirements of unsupervised anomaly detection algorithms. Six different algorithms are evaluated qualita-tively and finally a global k-NN approach was selected for a practical deployment. The new system was able to detect misconfigurations and gave the security operation center team more insight about processes in the network.
The size-dependent magnetic properties of small iron clusters deposited on ultrathin Ni/Cu(100) f... more The size-dependent magnetic properties of small iron clusters deposited on ultrathin Ni/Cu(100) films have been studied with circularly polarized synchrotron radiation. For x-ray magnetic circular dichroism studies, the magnetic moments of size-selected clusters were aligned perpendicular to the sample surface. Exchange coupling of the clusters to the ultrathin Ni/Cu(100) film determines the orientation of their magnetic moments. All clusters are
The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films... more The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films have been studied with circularly polarized synchrotron radiation. With the use of sum rules, orbital and spin magnetic moments have been extracted from x-ray magnetic circular dichroism spectra. The ratio of orbital to spin magnetic moments varies considerably with cluster size, reflecting the dependence of magnetic properties on cluster size and geometry. These variations can be explained in terms of enhanced orbital moments in small clusters.
Small, mass selected, deposited chromium clusters in the size range of 113 atoms per cluster hav... more Small, mass selected, deposited chromium clusters in the size range of 113 atoms per cluster have been investigated using x-ray absorption spectroscopy at the BESSY II storage ring at the chromium L 2,3 edges. The chromium clusters have been deposited on ultrathin iron films ...
We have studied the Ni L edge x-ray absorption fine structure for thin Ni films evaporated on a C... more We have studied the Ni L edge x-ray absorption fine structure for thin Ni films evaporated on a Cu(001) substrate. The measurements have been carried out for films having coverages ranging from 0.07 monolayers (ML) up to 3.1 ML . The coverage has been calibrated using the ...
Security Information and Event Management (SIEM) systems are today a key component of complex ent... more Security Information and Event Management (SIEM) systems are today a key component of complex enter-prise networks. They usually aggregate and correlate events from different machines and perform a rule-based analysis to detect threats. In this paper we present an enhancement of such systems which makes use of unsupervised anomaly detection algorithms without the need for any prior training of the system. For data acquisition, events are exported from an existing SIEM appliance, parsed, unified and preprocessed to fit the requirements of unsupervised anomaly detection algorithms. Six different algorithms are evaluated qualita-tively and finally a global k-NN approach was selected for a practical deployment. The new system was able to detect misconfigurations and gave the security operation center team more insight about processes in the network.
The size-dependent magnetic properties of small iron clusters deposited on ultrathin Ni/Cu(100) f... more The size-dependent magnetic properties of small iron clusters deposited on ultrathin Ni/Cu(100) films have been studied with circularly polarized synchrotron radiation. For x-ray magnetic circular dichroism studies, the magnetic moments of size-selected clusters were aligned perpendicular to the sample surface. Exchange coupling of the clusters to the ultrathin Ni/Cu(100) film determines the orientation of their magnetic moments. All clusters are
The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films... more The size-dependent magnetic properties of small iron clusters deposited on ultrathin nickel films have been studied with circularly polarized synchrotron radiation. With the use of sum rules, orbital and spin magnetic moments have been extracted from x-ray magnetic circular dichroism spectra. The ratio of orbital to spin magnetic moments varies considerably with cluster size, reflecting the dependence of magnetic properties on cluster size and geometry. These variations can be explained in terms of enhanced orbital moments in small clusters.
Small, mass selected, deposited chromium clusters in the size range of 113 atoms per cluster hav... more Small, mass selected, deposited chromium clusters in the size range of 113 atoms per cluster have been investigated using x-ray absorption spectroscopy at the BESSY II storage ring at the chromium L 2,3 edges. The chromium clusters have been deposited on ultrathin iron films ...
We have studied the Ni L edge x-ray absorption fine structure for thin Ni films evaporated on a C... more We have studied the Ni L edge x-ray absorption fine structure for thin Ni films evaporated on a Cu(001) substrate. The measurements have been carried out for films having coverages ranging from 0.07 monolayers (ML) up to 3.1 ML . The coverage has been calibrated using the ...
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Papers by Matthias Reif