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Construction of Nondeterministic Finite Automata
Stanek, Timotej ; Šimek, Václav (referee) ; Kaštil, Jan (advisor)
This thesis discuss about dilemma in construction of nondeterministic finite automata from PCRE expressions with respect of their parameters with use in Intrusion Detection Systems. There is showed PCRE expressions syntax too. We discussed two different approaches to construct nondeterministic finite automata from PCRE expressions. The implementation of these two algorithms is described. We constructed finite automata with them from expressions of three Intrusion Detection Systems: SNORT, Bro IDS and L7-Filter, and finally we compared their parameters and deduced conclusions.
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Automatic Grouping of Regular Expressions
Stanek, Timotej ; Kořenek, Jan (referee) ; Kaštil, Jan (advisor)
This project is about security of computer networks using Intrusion Detection Systems. IDS contain rules for detection expressed with regular expressions, which are for detection represented by finite-state automata. The complexity of this detection with non-deterministic and deterministic finite-state automata is explained. This complexity can be reduced with help of regular expressions grouping. Grouping algorithm and approaches for speedup and improvement are introduced. One of the approches is Genetic algorithm, which can work real-time. Finally Random search algorithm for grouping of regular expressions is presented. Experiment results with these approches are shown and compared between each other.
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Construction of Nondeterministic Finite Automata
Stanek, Timotej ; Šimek, Václav (referee) ; Kaštil, Jan (advisor)
This thesis discuss about dilemma in construction of nondeterministic finite automata from PCRE expressions with respect of their parameters with use in Intrusion Detection Systems. There is showed PCRE expressions syntax too. We discussed two different approaches to construct nondeterministic finite automata from PCRE expressions. The implementation of these two algorithms is described. We constructed finite automata with them from expressions of three Intrusion Detection Systems: SNORT, Bro IDS and L7-Filter, and finally we compared their parameters and deduced conclusions.
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Automatic Grouping of Regular Expressions
Stanek, Timotej ; Kořenek, Jan (referee) ; Kaštil, Jan (advisor)
This project is about security of computer networks using Intrusion Detection Systems. IDS contain rules for detection expressed with regular expressions, which are for detection represented by finite-state automata. The complexity of this detection with non-deterministic and deterministic finite-state automata is explained. This complexity can be reduced with help of regular expressions grouping. Grouping algorithm and approaches for speedup and improvement are introduced. One of the approches is Genetic algorithm, which can work real-time. Finally Random search algorithm for grouping of regular expressions is presented. Experiment results with these approches are shown and compared between each other.
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