arXiv subjects

Georg Carle

Publications and source records attributed to Georg Carle.

At least 73 records · Page 4Linked to original sources

arXiv2018

Trustworthy Configuration Management for Networked Devices using Distributed Ledgers

Numerous IoT applications, like building automation or process control of industrial sites, exist today. These applications inherently have a strong connection to the physical world. Hence, IT security threats cannot only cause problems like data leaks but also safety issues which might harm people. Attacks on IT systems are not only performed by outside attackers but also insiders like administrators. For this reason, we present ongoing work on a configuration management system (CMS) that provides control over administrators, restrains their rights, and enforces separation of concerns. We reach this goal by conducting a configuration management process that requires multi-party authorization for critical configurations to achieve Byzantine fault tolerance against attacks and faults by administrators. Only after a configuration has been authorized by multiple experts, it is applied to the targeted devices. For the whole configuration management process, our CMS guarantees accountability and traceability. Lastly, our system is tamper-resistant as we leverage Hyperledger Fabric, which provides a distributed execution environment for our CMS and a blockchain-based distributed ledger that we use to store the configurations. A beneficial side effect of this approach is that our CMS is also suitable to manage configurations for infrastructure shared across different organizations that do not need to trust each other.

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arXiv2018

A Management Framework for Secure Multiparty Computation in Dynamic Environments

Secure multiparty computation (SMC) is a promising technology for privacy-preserving collaborative computation. In the last years several feasibility studies have shown its practical applicability in different fields. However, it is recognized that administration and management overhead of SMC solutions are still a problem. A vital next step is the incorporation of SMC in the emerging fields of the Internet of Things and (smart) dynamic environments. In these settings, the properties of these contexts make utilization of SMC even more challenging since some of its vital premises regarding environmental stability and preliminary configuration are not initially fulfilled. We bridge this gap by providing FlexSMC, a management and orchestration framework for SMC which supports the discovery of nodes, supports a trust establishment between them and realizes robustness of SMC session by handling nodes failures and communication interruptions. The practical evaluation of FlexSMC shows that it enables the application of SMC in dynamic environments with reasonable performance penalties and computation durations allowing soft real-time and interactive use cases.

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arXiv2018

A Performance and Resource Consumption Assessment of Secure Multiparty Computation

In recent years, secure multiparty computation (SMC) advanced from a theoretical technique to a practically applicable technology. Several frameworks were proposed of which some are still actively developed. We perform a first comprehensive study of performance characteristics of SMC protocols using a promising implementation based on secret sharing, a common and state-of-the-art foundation. Therefor, we analyze its scalability with respect to environmental parameters as the number of peers, network properties -- namely transmission rate, packet loss, network latency -- and parallelization of computations as parameters and execution time, CPU cycles, memory consumption and amount of transmitted data as variables. Our insights on the resource consumption show that such a solution is practically applicable in intranet environments and -- with limitations -- in Internet settings.

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arXiv2018

Structure and Stability of Internet Top Lists

Active Internet measurement studies rely on a list of targets to be scanned. While probing the entire IPv4 address space is feasible for scans of limited complexity, more complex scans do not scale to measuring the full Internet. Thus, a sample of the Internet can be used instead, often in form of a "top list". The most widely used list is the Alexa Global Top1M list. Despite their prevalence, use of top lists is seldomly questioned. Little is known about their creation, representativity, potential biases, stability, or overlap between lists. As a result, potential consequences of applying top lists in research are not known. In this study, we aim to open the discussion on top lists by investigating the aptness of frequently used top lists for empirical Internet scans, including stability, correlation, and potential biases of such lists.

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arXiv2017

Software Distribution Transparency and Auditability

A large user base relies on software updates provided through package managers. This provides a unique lever for improving the security of the software update process. We propose a transparency system for software updates and implement it for a widely deployed Linux package manager, namely APT. Our system is capable of detecting targeted backdoors without producing overhead for maintainers. In addition, in our system, the availability of source code is ensured, the binding between source and binary code is verified using reproducible builds, and the maintainer responsible for distributing a specific package can be identified. We describe a novel "hidden version" attack against current software transparency systems and propose as well as integrate a suitable defense. To address equivocation attacks by the transparency log server, we introduce tree root cross logging, where the log's Merkle tree root is submitted into a separately operated log server. This significantly relaxes the inter-operator cooperation requirements compared to other systems. Our implementation is evaluated by replaying over 3000 updates of the Debian operating system over the course of two years, demonstrating its viability and identifying numerous irregularities.

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arXiv2017

HLOC: Hints-Based Geolocation Leveraging Multiple Measurement Frameworks

Geographically locating an IP address is of interest for many purposes. There are two major ways to obtain the location of an IP address: querying commercial databases or conducting latency measurements. For structural Internet nodes, such as routers, commercial databases are limited by low accuracy, while current measurement-based approaches overwhelm users with setup overhead and scalability issues. In this work we present our system HLOC, aiming to combine the ease of database use with the accuracy of latency measurements. We evaluate HLOC on a comprehensive router data set of 1.4M IPv4 and 183k IPv6 routers. HLOC first extracts location hints from rDNS names, and then conducts multi-tier latency measurements. Configuration complexity is minimized by using publicly available large-scale measurement frameworks such as RIPE Atlas. Using this measurement, we can confirm or disprove the location hints found in domain names. We publicly release HLOC's ready-to-use source code, enabling researchers to easily increase geolocation accuracy with minimum overhead.

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arXiv2017

Large-Scale Classification of IPv6-IPv4 Siblings with Variable Clock Skew

Linking the growing IPv6 deployment to existing IPv4 addresses is an interesting field of research, be it for network forensics, structural analysis, or reconnaissance. In this work, we focus on classifying pairs of server IPv6 and IPv4 addresses as siblings, i.e., running on the same machine. Our methodology leverages active measurements of TCP timestamps and other network characteristics, which we measure against a diverse ground truth of 682 hosts. We define and extract a set of features, including estimation of variable (opposed to constant) remote clock skew. On these features, we train a manually crafted algorithm as well as a machine-learned decision tree. By conducting several measurement runs and training in cross-validation rounds, we aim to create models that generalize well and do not overfit our training data. We find both models to exceed 99% precision in train and test performance. We validate scalability by classifying 149k siblings in a large-scale measurement of 371k sibling candidates. We argue that this methodology, thoroughly cross-validated and likely to generalize well, can aid comparative studies of IPv6 and IPv4 behavior in the Internet. Striving for applicability and replicability, we release ready-to-use source code and raw data from our study.

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arXiv2017

Privacy Assessment of Software Architectures based on Static Taint Analysis

Privacy analysis is critical but also a time-consuming and tedious task. We present a formalization which eases designing and auditing high-level privacy properties of software architectures. It is incorporated into a larger policy analysis and verification framework and enables the assessment of commonly accepted data protection goals of privacy. The formalization is based on static taint analysis and makes flow and processing of privacy-critical data explicit, globally as well as on the level of individual data subjects. Formally, we show equivalence to traditional label-based information flow security and prove overall soundness of our tool with Isabelle/HOL. We demonstrate applicability in two real-world case studies, thereby uncovering previously unknown violations of privacy constraints in the analyzed software architectures.

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arXiv2016

Scanning the IPv6 Internet: Towards a Comprehensive Hitlist

Active network measurements constitute an impor- tant part in gaining a better understanding of the Internet. Although IPv4-wide scans are now easily possible, random active probing is infeasible in the IPv6 Internet. Therefore, we propose a hybrid approach to generate a hitlist of IPv6 addresses for scanning: First, we extract IPv6 addresses from passive flow data. Second, we leverage publicly available resources such as rDNS data to gather further IPv6 addresses. Third, we conduct traceroute measurements from several vantage points to obtain additional addresses. We perform multiple active measurements on gathered IPv6 addresses and evaluate response rates over time. We extensively compare all IPv6 address sources. In total we found 150M unique IPv6 addresses over the course of four weeks. Our hitlist covers 72% of announced prefixes and 84% of Autonomous Systems. Finally, we give concrete recommendations to maximize source efficiency for different scan types.

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arXiv2016

HEAP: Reliable Assessment of BGP Hijacking Attacks

The detection of BGP prefix hijacking attacks has been the focus of research for more than a decade. However, state-of-the-art techniques fall short of detecting more elaborate types of attack. To study such attacks, we devise a novel formalization of Internet routing, and apply this model to routing anomalies in order to establish a comprehensive attacker model. We use this model to precisely classify attacks and to evaluate their impact and detectability. We analyze the eligibility of attack tactics that suit an attacker's goals and demonstrate that related work mostly focuses on less impactful kinds of attacks. We further propose, implement and test the Hijacking Event Analysis Program (HEAP), a new approach to investigate hijacking alarms. Our approachis designed to seamlessly integrate with previous work in order to reduce the high rates of false alarms inherent to these techniques. We leverage several unique data sources that can reliably disprove malicious intent. First, we make use of an Internet Routing Registry to derive business or organisational relationships between the parties involved in an event. Second, we use a topology-based reasoning algorithm to rule out events caused by legitimate operational practice. Finally, we use Internet-wide network scans to identify SSL/TLS-enabled hosts, which helps to identify non-malicious events by comparing public keys prior to and during an event. In our evaluation, we prove the effectiveness of our approach, and show that day-to-day routing anomalies are harmless for the most part. More importantly, we use HEAP to assess the validity of publicly reported alarms. We invite researchers to interface with HEAP in order to cross-check and narrow down their hijacking alerts.

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arXiv2016

Carrier-Grade Anomaly Detection Using Time-to-Live Header Information

Time-to-Live data in the IP header offers two interesting characteristics: First, different IP stacks pick different start TTL values. Second, each traversed router should decrement the TTL value. The combination of both offers host and route fingerprinting options. We present the first work to investigate Internet-wide TTL behavior at carrier scale and evaluate its fit to detect anomalies, predominantly spoofed source IP addresses. Using purpose-built software, we capture 2 weeks of raw TTL data at a 40 Gbit/s Internet uplink. For further insight, we actively measure observed hosts and conduct large-scale hitlist-based measurements, which yields three complementary data sets for IPv4 and IPv6. A majority (69% IPv4; 81% IPv6) of passively observed multi-packet hosts exhibit one stable TTL value. Active measurements on unstable hosts yield a stable anchor TTL value for more than 85% of responsive hosts. We develop a structure to further classify unstable hosts taking, for example, temporal stability into account. Correlation of TTL values with BGP data is clear, yet unpredictive. The results indicate that carrier-grade TTL anomaly detection can yield significant insights in the following categories: First, the method can flag anomalies based on TTL observations (yet likely at a difficult false positive/false negative trade-off). Second, the method can establish trust that a packet originates from its acclaimed source.

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arXiv2016

CAIR: Using Formal Languages to Study Routing, Leaking, and Interception in BGP

The Internet routing protocol BGP expresses topological reachability and policy-based decisions simultaneously in path vectors. A complete view on the Internet backbone routing is given by the collection of all valid routes, which is infeasible to obtain due to information hiding of BGP, the lack of omnipresent collection points, and data complexity. Commonly, graph-based data models are used to represent the Internet topology from a given set of BGP routing tables but fall short of explaining policy contexts. As a consequence, routing anomalies such as route leaks and interception attacks cannot be explained with graphs. In this paper, we use formal languages to represent the global routing system in a rigorous model. Our CAIR framework translates BGP announcements into a finite route language that allows for the incremental construction of minimal route automata. CAIR preserves route diversity, is highly efficient, and well-suited to monitor BGP path changes in real-time. We formally derive implementable search patterns for route leaks and interception attacks. In contrast to the state-of-the-art, we can detect these incidents. In practical experiments, we analyze public BGP data over the last seven years.

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arXiv2016

Adaptive Load-Aware Sampling for Network Monitoring on Multicore Commodity Hardware

Many current traffic monitoring systems employ deep packet inspection (DPI) in order to analyze network traffic. These systems include intrusion detection systems, software for network traffic accounting, traffic classification, or systems for monitoring service-level agreements. Traffic volumes and link speeds of current enterprise and ISP networks transform the process of inspecting traffic payload into a challenging task. In this paper we propose a novel adaptive sampling algorithm that selects the maximum number of packets from the network that the DPI system is able to consume. Our algorithm adapts its sampling rate according to the network traffic currently observed, and the number of packets that a monitoring application is able to process. It can be used in conjunction with current multicore-aware network traffic analysis setups, which allow for exploiting current multi-core hardware. We show the applicability of our algorithm with live-tests on a heavily used 10G link with real network monitoring tools.

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arXiv2016

Semantics-Preserving Simplification of Real-World Firewall Rule Sets

The security provided by a firewall for a computer network almost completely depends on the rules it enforces. For over a decade, it has been a well-known and unsolved problem that the quality of many firewall rule sets is insufficient. Therefore, there are many tools to analyze them. However, we found that none of the available tools could handle typical, real-world iptables rulesets. This is due to the complex chain model used by iptables, but also to the vast amount of possible match conditions that occur in real-world firewalls, many of which are not understood by academic and open source tools. In this paper, we provide algorithms to transform firewall rulesets. We reduce the execution model to a simple list model and use ternary logic to abstract over all unknown match conditions. These transformations enable existing tools to understand real-world firewall rules, which we demonstrate on four decently-sized rulesets. %After preparation with our algorithms, tools could understand them. Using the Isabelle theorem prover, we formally show that all our algorithms preserve the firewall's filtering behavior.

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arXiv2016

Verifying Security Policies using Host Attributes

For the formal verification of a network security policy, it is crucial to express the verification goals. These formal goals, called security invariants, should be easy to express for the end user. Focusing on access control and information flow security strategies, this work discovers and proves universal insights about security invariants. This enables secure and convenient auto-completion of host attribute configurations. We demonstrate our results in a civil aviation scenario. All results are machine-verified with the Isabelle/HOL theorem prover.

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arXiv2016

Demonstrating topoS: Theorem-Prover-Based Synthesis of Secure Network Configurations

In network management, when it comes to security breaches, human error constitutes a dominant factor. We present our tool topoS which automatically synthesizes low-level network configurations from high-level security goals. The automation and a feedback loop help to prevent human errors. Except for a last serialization step, topoS is formally verified with Isabelle/HOL, which prevents implementation errors. In a case study, we demonstrate topoS by example. For the first time, the complete transition from high-level security goals to both firewall and SDN configurations is presented.

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arXiv2016

MoonGen: A Scriptable High-Speed Packet Generator

We present MoonGen, a flexible high-speed packet generator. It can saturate 10 GbE links with minimum sized packets using only a single CPU core by running on top of the packet processing framework DPDK. Linear multi-core scaling allows for even higher rates: We have tested MoonGen with up to 178.5 Mpps at 120 Gbit/s. We move the whole packet generation logic into user-controlled Lua scripts to achieve the highest possible flexibility. In addition, we utilize hardware features of Intel NICs that have not been used for packet generators previously. A key feature is the measurement of latency with sub-microsecond precision and accuracy by using hardware timestamping capabilities of modern commodity NICs. We address timing issues with software-based packet generators and apply methods to mitigate them with both hardware support on commodity NICs and with a novel method to control the inter-packet gap in software. Features that were previously only possible with hardware-based solutions are now provided by MoonGen on commodity hardware. MoonGen is available as free software under the MIT license at https://github.com/emmericp/MoonGen

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arXiv2016

Certifying Spoofing-Protection of Firewalls

We present an algorithm to certify IP spoofing protection of firewall rulesets. The algorithm is machine-verifiably proven sound and its use is demonstrated in real-world scenarios.

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