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EEC 688/788 Secure and Dependable Computing Lecture 2 Wenbing Zhao Department of Electrical and Computer Engineering Cleveland State University

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Presentation on theme: "EEC 688/788 Secure and Dependable Computing Lecture 2 Wenbing Zhao Department of Electrical and Computer Engineering Cleveland State University"— Presentation transcript:

1 EEC 688/788 Secure and Dependable Computing Lecture 2 Wenbing Zhao Department of Electrical and Computer Engineering Cleveland State University

2 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Outline Basic terminology Dependability concepts  Attributes  Fault, error, and failure  Approaches to achieving dependability Security concepts  Attributes  Vulnerabilities, threats, attacks, and controls Computer Security: Art and Science, by Matt Bishop, Addison-Wesley Professional, 2002  Security in Computing, 4th Edition By Charles P. Pfleeger, Shari Lawrence Pfleeger 

3 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Terminology A system is an entity that interacts with other entities, i.e., other systems, including hardware, software, humans, and the physical world with its natural phenomena These other systems are the environment of the given system The system boundary is the common frontier between the system and its environment A system may consists of one or more components, such as nodes or processes System Environment System Boundary

4 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Terminology State: determines the status of the system  A system may be recovered to where it was before a failure if its state was captured and survives the failure Service delivered by a system: work done that benefits its users User/Client: another system that interacts with the former Function of a system: what the system is intended to do (Functional) Specification: description of the system function Correct service: when the delivered service implements the system function

5 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Dependability and its Attributes Dependability refers to the ability of a distributed system to provide correct services to its users despite various threats to the system such as undetected software defects, hardware failures, and malicious attacks A dependable system has the following attributes  Availability: a measure of the readiness of the system  Reliability: a measure of the system’s capability of providing correct services continuously for a period of time  Integrity: the capability of the system to protect its state from being compromised due to various threats  Maintainability: the capability of the system to evolve after it is deployed  Safety: when the system fails, it does not cause catastrophic consequences

6 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Quantitative Dependability Measures Availability - a measure of the readiness of the system  It is the probability of being operational at a given instant of time A availability means that the system is not operational at most one hour in a million hours A system with high availability may in fact fail. However, failure frequency and recovery time should be small enough to achieve the desired availability Soft real-time systems such as telephone switching and airline reservation require high availability

7 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao

8 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Quantitative Dependability Measures Reliability - a measure of continuous delivery of correct service.  It is the probability of surviving (potentially despite failures) over an interval of time  May also be evaluated as time to failure For example, the reliability requirement might be stated as a availability for a 10-hour mission. In other words, the probability of failure during the mission may be at most Hard real-time systems such as flight control and process control demand high reliability, in which a failure could mean loss of life

9 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Fault, Error, and Failure The adjudged or hypothesized cause of an error is called a fault An error is a manifestation of a fault in a system, in which the logical state of an element differs from its intended value A service failure occurs if the error propagates to the service interface and causes the service delivered by the system to deviate from correct service The failure of a component causes a permanent or transient fault in the system that contains the component Service failure of a system causes a permanent or transient external fault for the other system(s) that receive service from the given system

10 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Fault Faults can arise during all stages in a computer system's evolution - specification, design, development, manufacturing, assembly, and installation - and throughout its operational life Most faults that occur before full system deployment are discovered through testing and eliminated Faults that are not removed can reduce a system's dependability when it is in the field A fault can be classified by its duration, nature of output, and correlation to other faults (and many other criteria)

11 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Fault Types - Based on Duration Permanent faults are caused by irreversible device/software failures within a component due to damage, fatigue, or improper manufacturing, or bad design and implementation  Permanent software faults are also called Bohrbugs  Easier to detect Transient/intermittent faults are triggered by environmental disturbances or incorrect design  Transient software faults are also referred to as Heisenbugs  Study shows that Heisenbugs are the majority software faults  Harder to detect

12 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Fault Types - Based on Nature of Output Malicious fault: The fault that causes a unit to behave arbitrarily or malicious. Also referred to as Byzantine fault  A sensor sending conflicting outputs to different processors  Compromised software system that attempts to cause service failure Non-malicious faults: the opposite of malicious faults  Faults that are not caused with malicious intention  Faults that exhibit themselves consistently to all observers, e.g., fail-stop A fail-stop system simply stops executing once it fails Malicious faults are much harder to detect than non-malicious faults

13 Wenbing Zhao Fault Types - Based on Correlation Components fault may be independent of one another or correlated A fault is said to be independent if it does not directly or indirectly cause another fault Faults are said to be correlated if they are related. Faults could be correlated due to physical or electrical coupling of components Correlated faults are more difficult to detect than independent faults 5/8/2015 EEC688/788: Secure & Dependable Computing

14 5/8/2015 Wenbing Zhao Approaches to Achieving Dependability Fault Avoidance - how to prevent, by construction, the fault occurrence or introduction Fault Removal - how to minimize, by verification, the presence of faults Fault Tolerance - how to provide, by redundancy, a service complying with the specification in spite of faults Fault Forecasting - how to estimate, by evaluation, the presence, the creation, and the consequence of faults

15 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Computer Security and its Attributes Computer security is synonymous to the following three attributes:  Confidentiality: computer-related assets are accessed only by authorized parties. Confidentiality is sometimes called secrecy or privacy  Integrity: assets can be modified only by authorized parties or only in authorized ways  Availability: assets are accessible to authorized parties at appropriate times

16 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Confidentiality Confidentiality is the concealment of information  Conceal the content of the information  Conceal the very existence of information The need for keeping information secret arises from the government and the industry  Enforce “need to know” principle Achieve confidentiality: access control mechanisms  Cryptography: users without the cryptographic key cannot access unscrambled information  Other access control mechanisms may conceal the mere existence of data, such as Steganography

17 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Integrity Integrity refers to the trustworthiness of information, usually phrased in terms of preventing improper or unauthorized change  Data integrity: the content of the information  Origin integrity: the source of the data, i.e., authentication Integrity mechanisms:  Prevention mechanisms: Blocking any unauthorized attempts to change the data Blocking any attempts to change the data in unauthorized ways  Detection mechanisms: report that the data’s integrity is no longer trustworthy Analyze system events to detect problems Analyze the data itself to see if required or expected constraints still hold

18 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Working with Confidentiality & Integrity With confidentiality, the data is either compromised or it is not With integrity, both the correctness and the trustworthiness of the data must be considered  Origin of the data  How well the data was protected before it arrived at the current machine  How well the data is protected on the current machine Evaluating integrity is often very difficult

19 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Availability Availability refers to the ability to use the information desired  An aspect of reliability  Also an aspect of system design: an unavailable system is at least as bad as no system at all Why availability is relevant to security?  Someone may deliberately arrange to deny access to data or to a service by making it unavailable  Denial of service attacks: attempts to block availability  It is very difficulty to detect denial of service attacks Must determine if the unusual access patterns are attributable to deliberate manipulation of resources or of environment (i.e., an atypical event)

20 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Availability The security community is just beginning to understand what availability implies and how to ensure it A small, centralized control of access is fundamental to preserving confidentiality and integrity, but it is not clear that a single access control point can enforce availability Much of computer security's past success has focused on confidentiality and integrity; full implementation of availability is security's next great challenge

21 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Relationship of Security Goals A secure system must meet all three requirements The challenge is how to find the right balance among the goals, which often conflict  For example, it is easy to preserve a particular object's confidentiality in a secure system simply by preventing everyone from reading that object  However, this system is not secure, because it does not meet the requirement of availability for proper access => There must be a balance between confidentiality and availability

22 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Relationship of Security Goals

23 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Vulnerabilities, Threats, Attacks, & Controls A vulnerability is a weakness in the security system A threat to a computing system is a set of circumstances that has the potential to cause loss or harm A human who exploits a vulnerability perpetrates an attack on the system. How do we address these problems? We use a control as a protective measure  A control is an action, device, procedure, or technique that removes or reduces a vulnerability  A threat is blocked by control of a vulnerability

24 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Threats, Vulnerabilities, and Controls

25 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Type of Threats An interception means that some unauthorized party has gained access to an asset In an interruption, an asset of the system becomes lost, unavailable, or unusable If an unauthorized party not only accesses but tampers with an asset, the threat is a modification An unauthorized party might create a fabrication of counterfeit objects on a computing system

26 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Type of Threats

27 5/8/2015 EEC688/788: Secure & Dependable Computing Wenbing Zhao Threats: Methods, Opportunity, and Motive A malicious attacker must have three things:  Method: the skills, knowledge, tools, and other things with which to launch an attack  Opportunity: the time and access to accomplish the attack  Motive: a reason to want to perform this attack against this system

28 5/8/2015 EEC688: Secure & Dependable Computing Wenbing Zhao Methods of Defense Harm occurs when a threat is realized against a vulnerability To protect against harm, we can neutralize the threat, close the vulnerability, or both The possibility for harm to occur is called risk

29 5/8/2015 EEC688: Secure & Dependable Computing Wenbing Zhao Methods of Defense We can deal with harm in several ways. We can seek to  Prevent it, by blocking the attack or closing the vulnerability  Deter it, by making the attack harder, but not impossible  Deflect it, by making another target more attractive (or this one less so)  Detect it, either as it happens or some time after the fact  Recover from its effects Intrusion tolerance is also a form of recovery because it enables the system to continue operating correctly despite attacks

30 5/8/2015 EEC688: Secure & Dependable Computing Wenbing Zhao Methods of Defense – Multiple Controls

31 5/8/2015 EEC688: Secure & Dependable Computing Wenbing Zhao Countermeasures / Controls Encryption  Scrambling process Software controls  Internal program controls, OS controls, development controls Hardware controls  hardware or smart card implementations of encryption Policies and Procedures  Example: change password periodically Physical Controls  Example: Locks on doors, guards at entry points


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