Orbital photogalvanic effects in quantum-confined structures

We report on the circular and linear photogalvanic effects caused by free-carrier absorption of terahertz radiation in electron channels on (001)-oriented and miscut silicon surfaces. The photocurrent behavior upon variation of the radiation polarization state, wavelength, gate voltage and temperature is studied. We present the microscopical and phenomenological theory of the photogalvanic effects, which describes well the experimental results. In particular, it is demonstrated that the circular (photon-helicity sensitive) photocurrent in silicon-based structures is of pure orbital nature originating from the quantum interference of different pathways contributing to the absorption of monochromatic radiation.Comment: 8 pages, 5 figures, two culumne

Observation of orbital circular photogalvanic effect

We report on the observation of the circular photogalvanic effect in Si-metal-oxide-semiconductor fieldeffect transistors with inversion channel excited by terahertz radiation. We demonstrate that in spite of the fact that the photocurrent is caused by transfer of the photon angular momentum to free carriers, it is not due to spin orientation but has a pure orbital origin. It results from the quantum interference of different pathways contributing to the free-carrier absorption of monochromatic radiation

Extending The Sleuth Kit and its underlying model for pooled storage file system forensic analysis

Carrier's book File System Forensic Analysis is one of the most comprehensive sources when it comes to the forensic analysis of file systems. Published in 2005, it provides details about the most commonly used file systems of that time as well as a process model to analyze file systems in general. The Sleuth Kit is the implementation of Carrier's model and it is still widely used during forensic analyses today—standalone or as a basis for forensic suites such as Autopsy. While The Sleuth Kit is still actively maintained, the model has not seen any updates since then. Moreover, there is no support for modern file systems implementing new paradigms such as pooled storage. In this paper, we present an update to Carrier's model which enables the analysis of pooled storage file systems. To demonstrate that our model is suitable, we implemented it for ZFS—a file system for large scale storage, cloud, and virtualization environments—and show how to perform an analysis of this file system using our model and extended toolkit

A comprehensive measurement study of domain generating malware

Recent years have seen extensive adoption of domain generation algorithms (DGA) by modern botnets. The main goal is to generate a large number of domain names and then use a small subset for actual C&C communication. This makes DGAs very compelling for botmasters to harden the infrastructure of their botnets and make it resilient to blacklisting and attacks such as takedown efforts. While early DGAs were used as a backup communication mechanism, several new botnets use them as their primary communication method, making it extremely important to study DGAs in detail. In this paper, we perform a comprehensive measurement study of the DGA landscape by analyzing 43 DGA-based malware families and variants. We also present a taxonomy for DGAs and use it to characterize and compare the properties of the studied families. By reimplementing the algorithms, we pre-compute all possible domains they generate, covering the majority of known and active DGAs. Then, we study the registration status of over 18 million DGA domains and show that corresponding malware families and related campaigns can be reliably identified by pre-computing future DGA domains. We also give insights into botmasters' strategies regarding domain registration and identify several pitfalls in previous takedown efforts of DGA-based botnets. We will share the dataset for future research and will also provide a web service to check domains for potential DGA identity