- KonferenzbeitragTowards secure and reliable firewall systems based on MINIX 3(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Weis, Rüdiger; Schüler, Brian; Flemming, Stefan A.; Freiling, Felix C.Minix 3 is a real micro kernel operation system with a lot of remarkable security features. Two of the main points are size and isolation. The Minix 3 kernel is less than one thousand times the size of Linux. All drivers and the IP stack live in user land. We show a port of the netfilter framework, which leads to a system with better stability and security than the widely used Linux solutions [We07]. Additionally we present some new ideas regarding virtualized systems.
- KonferenzbeitragA transparent Bridge for forensic sound network traffic data acquisition(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Kiltz, Stefan; Hildebrandt, Mario; Altschaffel, Robert; Dittmann, Jana; Freiling, Felix C.In this paper we introduce a prototype that is designed to produce forensic sound network data recordings using inexpensive hardand software, the Linux Forensic Transparent Bridge (LFTB). It supports the investigation of the network communication parameters and the investigation of the payload of network data. The basis for the LFTB is a self-developed model of the forensic process which also addresses forensically relevant data types and considerations for the design of forensic software using software engineering techniques. LFTB gathers forensic evidence to support cases such as malfunctioning hardand software and for investigating malicious activity. In the latter application the stealthy design of the proposed device is beneficial. Experiments as part of a first evaluation show its usability in a support case and a malicious activity scenario. Effects to latency and throughput were tested and limitations for packet recording analysed. A live monitoring scheme warning about potential packet loss endangering evidence has been implemented.
- KonferenzbeitragA parallel computing system with specialized coprocessors for cryptanalytic algorithms(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Kastl, Wolfgang; Loimayr, Thomas; Freiling, Felix C.In this paper we present a scalable, parallel computing system consisting of specialized processors primarily designed for the implementation of cryptanalytic algorithms. Even though the system was developed in regard to solve cryptanalytic problems, it is suitable for many other tasks which can benefit from the enormous computing power of the system (e.g. malware analysis). In addition to the use of multi-core CPUs, the computing system takes advantage of graphic cards (GPUs) and FPGAs as specialized coprocessors. Thus, it gains an edge over other conventional parallel computing systems.
- KonferenzbeitragSocial Lending aus der Perspektive des Datenschutzes(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Böhme, Rainer; Pötzsch, Stefanie; Freiling, Felix C.Als Social Lending bezeichnet man die Kreditvergabe zwischen Privatpersonen. Beim Online Social Lending veröffentlichen potenzielle Kreditnehmer ihre Gesuche auf entsprechenden Webseiten im Internet, um private Investoren zu finden. Dieser Beitrag weist auf einen Konflikt zwischen wirtschaftlichen Interessen und Datenschutzzielen hin und analysiert ihn mit empirischen Daten der größten deutschen Social-Lending-Plattform Smava.de. Der Analyse zufolge lohnt es sich gegenwärtig nicht, mehr personenbezogene Daten zu veröffentlichen als unbedingt notwendig.
- KonferenzbeitragA fuzzy model for IT security investments(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Schryen, Guido; Freiling, Felix C.This paper presents a fuzzy set based decision support model for taking uncertainty into account when making security investment decisions for distributed systems. The proposed model is complementary to probabilistic approaches and useful in situations where probabilistic information is either unavailable or not appropriate to reliably predict future conditions. We first present the specification of a formal security language that allows to specify under which conditions a distributed system is protected against security violations. We show that each term of the security language can be transformed into an equivalent propositional logic term. Then we use propositional logic terms to define a fuzzy set based decision model. This optimization model incorporates uncertainty with regard to the impact of investments on the achieved security levels of components of the distributed system. The model also accounts for budget and security constraints, in order to be applicable in practice.
- Editiertes BuchSicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit(2010) Freiling, Felix C.
- KonferenzbeitragCAPTCHAs: the good, the bad, and the ugly(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Baecher, Paul; Fischlin, Marc Gordon Lior; Langenberg, Robert; Lützow, Michael; Schröder, Dominique; Freiling, Felix C.A CAPTCHA is a program that generates challenges that are easy to solve for humans but difficult to solve for computers. The most common CAPTCHAs today are text-based ones where a short word is embedded in a cluttered image. In this paper, we survey the state-of-the-art of currently deployed CAPTCHAs, especially of some popular German sites. Surprisingly, despite their importance and the largescale deployment, most of the CAPTCHAs like the ones of the "Umweltprämie", the Bundesfinanzagentur, and the Sparda-Bank are rather weak. Our results show that these CAPTCHAs are subject to automated attacks solving up to 80% of the puzzles. Furthermore, we suggest design criteria for "good" CAPTCHAs and for the system using them. In light of this we revisit the popular reCAPTCHA system and latest developments about its security. Finally, we discuss some alternative approaches for CAPTCHAs.
- KonferenzbeitragQuantifying the attack surface of a web application(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Heumann, Thomas; Keller, Jörg; Türpe, Sven; Freiling, Felix C.The attack surface of a system represents the exposure of application objects to attackers and is affected primarily by architecture and design decisions. Given otherwise consistent conditions, reducing the attack surface of a system or an application is expected to reduce its overall vulnerability. So far, only systems have been considered but not single applications. As web applications provide a large set of applications built upon a common set of concepts and technologies, we choose them as an example, and provide qualitative and quantitative indicators. We propose a multidimensional metric for the attack surface of web applications, and discuss the rationale behind. Our metric is easy to use. It comprises both a scalar numeric indicator for easy comparison and a more detailed vector representation for deeper analysis. The metric can be used to guide security testing and development. We validate the applicability and suitability of the metric with popular web applications, of which knowledge about their vulnerability already exists.
- KonferenzbeitragSecurity analysis of OpenID(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Sovis, Pavol; Kohlar, Florian; Schwenk, Jörg; Freiling, Felix C.OpenID is a user-centric and decentralized Single Sign-On system. It enables users to sign into Relying Partiesby providing an authentication assertion from an OpenID Provider. It is supported by many leading internet companies and there are over a billion accounts capable of using OpenID. We present a security analysis of OpenID and the corresponding extensions and reveal several vulnerabilities. This paper demonstrates how identity information sent within the OpenID protocol can be manipulated, due to an improper verification of OpenID assertions and no integrity protection of the authentication request.
- KonferenzbeitragQuantitative model-based safety analysis: a case study(Sicherheit 2010. Sicherheit, Schutz und Zuverlässigkeit, 2010) Güdemann, Matthias; Ortmeier, Frank; Freiling, Felix C.The rising complexity of many safety-critical systems necessitates new analysis methods. Model-based safety analysis approaches aim at finding critical failure combinations by analysis of models of the whole system (i.e. software, hardware, and failure modes). The big advantage of these methods compared to traditional approaches is that the results are of very high significance. Until now, model-based approaches have only to a limited extent been applied to answer quantitative questions in safety analysis. Model-based approaches in this context are often limited to analysis of specific failure propagation models. They do not include system dynamics and behavior. A consequence is, that the methods are very error-prone because of wrong assumptions. New achievements in the domain of (probabilistic) model-checking now allow for overcoming this problem. This paper illustrates how such an approach for quantitative model-based safety analysis is used to model and analyze a real-world case study from the railway domain.