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UI CS 448 - Lecture Notes

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This discussion is based on the paper:Basic Concepts and Taxonomy of Dependable and Secure Computing,Algirdas Avizienis, Jean-Claude Laprie, Brian Randell, and Carl Landwehr, IEEE TRANSACTIONS ON DEPENDABLE AND SECURE COMPUTING,! VOL. 1,!NO. 1,! JANUARY-MARCH 200412BasicsWe have discussed the basic issues in the second part of Sequence 8Now we will focus on more survivability related issues of the aforementioned paperMost of the material is directly taken from the paper and (to avoid visual clutter) will not be explicitly cited!3Threats to Dependability and SecuritySystem Life Cycle: Phases and EnvironmentDevelopment phaseDevelopment Environment of system consists ofphysical world with its natural phenomenahuman developers (+lacking competence,malicious objective)development tools: software and hardwareproduction and test facilities43) Threats to Dependability and Security3.1: System Life Cycle: Phases and EnvironmentDevelopment phaseDevelopment Environment of system consists ofphysical world with its natural phenomenahuman developers (+lacking competence,malicious objective)development tools: software and hardwareproduction and test facilities53) Threats to Dependability and SecurityUse phaseSystem is accepted for use and starts delivering services1. Service delivery2. Service outage3. Service shutdownMaintenance may take place during all three periods of use phase6Use Environment elements:Physical world: with its natural phenomenaAdministrators (includes maintainers): have authority to manage, modify, repair and use system. Some authorized humans may lack competence of have malicious objectives7Use Environment elements:Users: humans or other system that receive services Providers: humans or other systems that deliver servicesInfrastructure: entities that provide services to the system, e.g., information sources (time, GPS) communications equipment/links, power, cooling etc.8Use Environment elements:Intruders: malicious entities (human or other systems)attempt to exceed authority they havealter serviceshalt themalter system’s functionality or performanceaccess confidential informationexamples: hackers, vandals, corrupt insiders, governments, malicious software9Maintenance3.2 Faults3.2.1 A Taxonomy of FaultsAll faults that may affect a system during its life areclassified according to eight basic viewpoints, leading to theelementary fault classes, as shown in Fig. 4.If all combinations of the eight elementary fault classeswere possible, there would be 256 different combined faultclasses. However, not all criteria are applicable to all faultclasses; for example, natural faults cannot be classified byobjective, intent, and capability. We have identified 31 likelycombinations; they are shown in Fig. 5.More combinations may be identified in the future. Thecombined fault classes of Fig. 5 are shown to belong to threemajor partially overlapping groupings:. development faults that include all fault classesoccurring during development,. physical faults that include all fault classes thataffect hardware,. interaction faults that include all external faults.The boxes at the bottom of Fig. 5a identify the names ofsome illustrative fault classes.Knowledge of all possible fault classes allows the user todecide which classes should be included in a dependabilityand security specification. Next, we comment on the faultclasses that are shown in Fig. 5. Fault numbers (1 to 31) willbe used to relate the discussion to Fig. 5.3.2.2 On Natural FaultsNatural faults (11-15) are physical (hardware) faults that arecaused by natural phenomena without human participation.We note that humans also can cause physical faults (6-10,16-23); these are discussed below. Production defects (11) arenatural faults that originate during development. Duringoperation the natural faults are either internal (12-13), due tonat ural proc esses that cause physical de terioration, orexternal (14-15), due to natural processes that originateoutside the system boundaries and cause physical inter-ference by penetrating the hardware boundary of the system(radiation, etc.) or by entering via use interfaces (powertransients, noisy input lines, etc.).3.2.3 On Human-Made FaultsThe definition of human-made faults (that result from humanactions) includes absence of actions when actions should beperfor me d, i.e ., omission faults,orsimplyomissions.Performing wrong actions leads to commission faults.AVI!ZZIENIS ET AL.: BASIC CONCEPTS AND TAXONOMY OF DEPENDABLE AND SECURE COMPUTING 15Fig. 3. The various forms of maintenance.Fig. 4. The elementary fault classes.10Faults: OverviewFig:4elementaryfault classes3.2 Faults3.2.1 A Taxonomy of FaultsAll faults that may affect a system during its life areclassified according to eight basic viewpoints, leading to theelementary fault classes, as shown in Fig. 4.If all combinations of the eight elementary fault classeswere possible, there would be 256 different combined faultclasses. However, not all criteria are applicable to all faultclasses; for example, natural faults cannot be classified byobjective, intent, and capability. We have identified 31 likelycombinations; they are shown in Fig. 5.More combinations may be identified in the future. Thecombined fault classes of Fig. 5 are shown to belong to threemajor partially overlapping groupings:. development faults that include all fault classesoccurring during development,. physical faults that include all fault classes thataffect hardware,. interaction faults that include all external faults.The boxes at the bottom of Fig. 5a identify the names ofsome illustrative fault classes.Knowledge of all possible fault classes allows the user todecide which classes should be included in a dependabilityand security specification. Next, we comment on the faultclasses that are shown in Fig. 5. Fault numbers (1 to 31) willbe used to relate the discussion to Fig. 5.3.2.2 On Natural FaultsNatural faults (11-15) are physical (hardware) faults that arecaused by natural phenomena without human participation.We note that humans also can cause physical faults (6-10,16-23); these are discussed below. Production defects (11) arenatural faults that originate during development. Duringoperation the natural faults are either internal (12-13), due tonatural processes that cause ph ysical deterioration, orexternal (14-15), due to natural processes that originateoutside the system boundaries and cause physical inter-ference by penetrating the hardware boundary of the


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UI CS 448 - Lecture Notes

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