34315877
Detecting Disruptive Routers in Wireless Sensor Networks
In wireless sensor networks, sensor nodes are typically resource constrained and used as routers to forward packets for other nodes. Compromised sensor nodes may be able to cause network-wide denial of service by dropping or corrupting packets. This paper presents a novel, lightweight approach for detecting disruptive routers that drop or corrupt packets.
12589493
Automatic analysis of firewall and network intrusion detection system configurations
Given a network that deploys multiple firewalls and network intrusion detection systems (NIDSs), ensuring that these security components are correctly configured is a challenging problem. Although models have been developed to reason independently about the effectiveness of firewalls and NIDSs, there is no common framework to analyze their interaction. This paper presents an integrated, constraint-based approach for modeling and reasoning about these configurations. Our approach considers the dependencies among the two types of components, and can reason automatically about their combined behavior. We have developed a tool for the specification and verification of networks that include multiple firewalls and NIDSs, based on this approach. This tool can also be used to automatically generate NIDS configurations that are optimal relative to a given cost function.
18650610
Modeling multistep cyber attacks for scenario recognition
Efforts toward automated detection and identification of multistep cyber attack scenarios would benefit significantly from a methodology and language for modeling such scenarios. The Correlated Attack Modeling Language (CAML) uses a modular approach, where a module represents an inference step and modules can be linked together to detect multistep scenarios. CAML is accompanied by a library of predicates, which functions as a vocabulary to describe the properties of system states and events. The concept of attack patterns is introduced to facilitate reuse of generic modules in the attack modeling process. CAML is used in a prototype implementation of a scenario recognition engine that consumes first-level security alerts in real time and produces reports that identify multistep attack scenarios discovered in the alert stream.
10409164
Denial of service against the Domain Name System
Because many network services rely on the Domain Name System, denial-of-service attacks against it can be particularly damaging. This article analyzes such threats and reviews existing and proposed countermeasures for addressing them.
42848873
Time Lower Bounds for Permutation Routing on Multi-Dimensional Bused Meshes
We present time lower bounds for the permutation routing problem on three- and higher-dimensional n x…x n meshes with buses. We prove an (r–1)n/r lower bound for the general case of an r-dimensional bused mesh, r≥2, which is not as strong for low-dimensional as for higher-dimensional cases. We then use a different approach to construct a 0.705n lower bound for the three-dimensional case.
15843617
Routing with Locality on Meshes with Buses
Routing with locality is studied for meshes with buses. In this problem, packets' distances are bounded by a value,d, which is less than the diameter of the network. This problem arises naturally when specific known algorithms are implemented on meshes. Solving this problem in ordinary meshes requires at least a routing time ofdsteps. To do better than this, we propose adding a kind of short bus to ordinary meshes. By using a technique which we call iterative walk-and-ride, we show how the routing time can be reduced by approximately one-third for solving the problem (including the multipacket version) on one- and two-dimensional short-bus meshes. The bounds we develop are tight.
30482723
Efficient video similarity measurement with video signature
The proliferation of video content on the Web makes similarity detection an indispensable tool in Web data management, searching, and navigation. We propose a number of algorithms to efficiently measure video similarity. We define video as a set of frames, which are represented as high dimensional vectors in a feature space. Our goal is to measure ideal video similarity (IVS), defined as the percentage of clusters of similar frames shared between two video sequences. Since IVS is too complex to be deployed in large database applications, we approximate it with Voronoi video similarity (VVS), defined as the volume of the intersection between Voronoi cells of similar clusters. We propose a class of randomized algorithms to estimate VVS by first summarizing each video with a small set of its sampled frames, called the video signature (ViSig), and then calculating the distances between corresponding frames from the two ViSigs. By generating samples with a probability distribution that describes the video statistics, and ranking them based upon their likelihood of making an error in the estimation, we show analytically that ViSig can provide an unbiased estimate of IVS. Experimental results on a large dataset of Web video and a set of MPEG-7 test sequences with artificially generated similar versions are provided to demonstrate the retrieval performance of our proposed techniques.
9354416
Verification of liveness properties using compositional reachability analysis
The software architecture of a distributed program can be represented by a hierarchical composition of subsystems, with interacting processes at the leaves of the hierarchy. Compositional reachability analysis (CRA) is a promising state reduction technique which can be automated and used to derive in stages the overall behaviour of a distributed program based on its architecture. Conventional CRA however has a limitation. The properties available for analysis after composition and reduction are constrained by the set of actions that remain globally observable. The liveness properties which involve internal actions of subsystems may therefore not be analysed. In this paper, we extend compositional reachability analysis to check liveness properties which may involve actions that are not globally observable. In particular, our approach permits the hiding of actions independently of the liveness properties that are to be verified in the final graph. In addition, it supports the simultaneous checking of multiple properties (both liveness and safety), and identifies those properties that are violated. The effectiveness of the extended technique is illustrated using a case study of a Reliable Multicast Transport Protocol (RMTP) with over 96,000 states and 660,000 transitions.
356082
Insensitive bounds for the moments of the sojourn time distribution in the M/G/1 processor-sharing queue
This paper studies the M/G/1 processor-sharing (PS) queue, in particular the sojourn time distribution conditioned on the initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are not suitable for computational purposes. This paper derives readily applicable insensitive bounds for all moments of the conditional sojourn time distribution. The instantaneous sojourn time, i.e., the sojourn time of an infinitesimally small job, leads to insensitive upper bounds requiring only knowledge of the traffic intensity and the initial job size. Interestingly, the upper bounds involve polynomials with so-called Eulerian numbers as coefficients. In addition, stochastic ordering and moment ordering results for the sojourn time distribution are obtained.
1708697
Enhancing compositional reachability analysis with context constraints
Compositional techniques have been proposed for traditional reachability analysis in order to introduce modularity and to control the state explosion problem. While modularity has been achived, state explosion is still a problem. Indeed, this problem may even be exacerbated as a locally minimised subsystem may contain many states and transitions forbidden by its context or environments. This paper presents a method to alleviate this problem effectively by including context constraints in local subsystem minimisation. The global behaviour generated using the method is observationally equivalent to that generated by compositional reachability analysis without the inclusion of context constraints.Context constraints, specified as interface processes, are restrictions imposed by the environment on subsystem behaviour. The minimisation produces a simplified machine that describes the behaviour of the subsystem constrained by its context. This machine can also be used as a substitute for the original subsystem in the subsequent steps of the compositional reachability analysis. Interface processes capturing context constraints can be specified by users or automatically constructd using a simple algorithm. The concepts in the paper are illustrated with a clients/server system.
5323690
Decomposing the queue length distribution of processor-sharing models into queue lengths of permanent customer queues
We obtain a decomposition result for the steady state queue length distribution in egalitarian processor-sharing (PS) models. In particular, for multi-class egalitarian PS queues, we show that the marginal queue length distribution for each class equals the queue length distribution of an equivalent single class PS model with a random number of permanent customers. Similarly, the mean sojourn time (conditioned on the initial service requirement) for each class can be obtained by conditioning on the number of permanent customers. The decomposition result implies linear relations between the marginal queue length probabilities, which also hold for other PS models such as the egalitarian PS models with state-dependent system capacity that only depends on the total number of customers in the system. Based on the exact decomposition result for egalitarian PS queues, we propose a similar decomposition for discriminatory processor-sharing (DPS) models, and numerically show that the approximation is accurate for moderate differences in service weights.