ing WS1S Systems to Verify Parameterized Networks . . . . . . . . . . . . 188 Kai Baukus, Saddek Bensalem, Yassine Lakhnech and Karsten Stahl FMona: A Tool for Expressing Validation Techniques over Infinite State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 J.-P. Bodeveix and M. Filali Transitive Closures of Regular Relations for Verifying Infinite-State Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220 Bengt Jonsson and Marcus Nilsson Diagnostic and Test Generation Using Static Analysis to Improve Automatic Test Generation . . . . . . . . . . . . . 235 Marius Bozga, Jean-Claude Fernandez and Lucian Ghirvu Efficient Diagnostic Generation for Boolean Equation Systems . . . . . . . . . . . . 251 Radu Mateescu Efficient Model-Checking Compositional State Space Generation with Partial Order Reductions for Asynchronous Communicating Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 Jean-Pierre Krimm and Laurent Mounier Checking for CFFD-Preorder with Tester Processes . . . . . . . . . . . . . . . . . . . . . . . 283 Juhana Helovuo and Antti Valmari Fair Bisimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 Thomas A. Henzinger and Sriram K. Rajamani Integrating Low Level Symmetries into Reachability Analysis . . . . . . . . . . . . . 315 Karsten Schmidt Model-Checking Tools Model Checking Support for the ASM High-Level Language . . . . . . . . . . . . . . 331 Giuseppe Del Castillo and Kirsten Winter Table of

Tools and Algorithms for the Construction and Analysis of Systems. Proc. TACAS 2009

Denial-of-Service (DoS) attacks pose a significant threat to the Internet today especially if they are distributed, i.e., launched simultaneously at a large number of systems. Reactive techniques that try to detect such an attack and throttle down malicious traffic prevail today but usually require an additional infrastructure to be really effective. In this paper we show that preventive mechanisms can be as effective with much less effort: We present an approach to (distributed) DoS attack prevention that is based on the observation that coordinated automated activity by many hosts needs a mechanism to remotely control them. To prevent such attacks, it is therefore possible to identify, infiltrate and analyze this remote control mechanism and to stop it in an automated fashion. We show that this method can be realized in the Internet by describing how we infiltrated and tracked IRC-based botnets which are the main DoS technology used by attackers today.

/pdf/botnet-tracking-exploring-a-root-cause-methodology-to-1wi7rkwdd2.pdf

Botnet tracking: exploring a root-cause methodology to prevent distributed denial-of-service attacks

A tutorial on EMPA: a theory of concurrent processes with nondeterminism, priorities, probabilities and time

A standard process algebra is extended by a new action ? which is meant to denote idling until the next clock cycle. A semantic theory based on testing is developed for the new language. This is characterised in terms of barbs, a variety of ready traces and also characterised as the initial theory generated by a set of equations.

A Process Algebra for Timed Systems

This paper shows how to put time into Milner's CCS to model real time systems. In particular, we will develop an expansion theorem for real time concurrency, which is an extension of the expansion theorem of CCS. The essential step made in this work is that a more general form of action prefix, μ@t.P is introduced, where t is a time variable. Intuitively, μ@t.P is an agent which may perform μ and become P[d/t] in doing so, where t is replaced by d, the time delay before μ is actually performed. The original form μ.P of action prefix of CCS is just a simple case of μ@t.P when t does not occur free in P — P does not depend on the time at which μ is performed.

CCS + Time = An Interleaving Model for Real Time Systems

Formal Techniques for Networked and Distributed Systems - FORTE 2004

Decidability and complexity of Petri nets with unordered data

TIC: A Timed Calculus for LOTOS

We study the relationship between name creation and replication in a setting of infinite-state communicating automata. By name creation we mean the capacity of dynamically producing pure names, with no relation between them other than equality or inequality. By replication we understand the ability of systems of creating new parallel identical threads, that can synchronize with each other. We have developed our study in the framework of Petri nets, by considering several extensions of P/T nets. In particular, we prove that in this setting name creation and replication are equivalent, but only when a garbage collection mechanism is added for idle threads. However, when simultaneously considering both extensions the obtained model is, a bit surprisingly, Turing complete and therefore, more expressive than when considered separately.

http://antares.sip.ucm.es/frosa/docs/fi08.pdf

Name creation vs. replication in Petri net systems

In this paper we study the extension of classical testing theory to a probabilistic process algebra. We consider a generative interpretation of probabilities for a language with two choice operators (one internal and the other external), which are annotated with a probability p e (0, 1). We define a testing semantics for our language, and we write P pass p T to denote that the process P passes the test T with a probability p. We also give a set of essential tests which has the same strength as the full family of tests.Next we give an alternative characterization of the testing semantics, based on the idea of acceptance sets, and we prove that the new equivalence is equal to the testing equivalence. Finally, we present a fully abstract denotational semantics based on acceptance trees.

David de Frutos-Escrig

Papers

Formal Techniques for Networked and Distributed Systems - FORTE 2004

Decidability and complexity of Petri nets with unordered data

TIC: A Timed Calculus for LOTOS

Name creation vs. replication in Petri net systems

Acceptance Trees for Probabilistic Processes