1. Computer Security Introduction
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2. Basic Components Confidentiality: Concealment of information
(prevent unauthorized disclosure of information).
Integrity: Trustworthiness of data/resources
(prevent unauthorized modifications).
Data integrity
Origin integrity (authentication)
Availability: Ability to use information/resources.
(prevent unauthorized withholding of
information/resources).
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3. Basic Components Additionally:
Authenticity, accountability, reliability, safety,
dependability, survivability . . .
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4. Confidentiality Historically, security is closely linked to secrecy.
Security involved a few organizations dealing mainly
with classified data.
However, nowadays security extends far beyond
confidentiality.
Confidentiality involves:
privacy: protection of private data,
secrecy: protection of organizational data.
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5. Integrity “Making sure that everything is as it is supposed to be.”
For Computer Security this means:
Preventing unauthorized writing or modifications.
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6. Availability For Computer Systems this means that:
Services are accessible and useable (without undue
Delay) whenever needed by an authorized entity.
For this we need fault-tolerance.
Faults may be accidental or malicious (Byzantine).
Denial of Service attacks are an example of malicious
attacks.
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7. Relationship between Confidentiality Integrity and Availability
Secure
Availability
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8. Other security requirements
Reliability – deals with accidental damage,
Safety – deals with the impact of system failure caused by the environment,
Dependability – reliance can be justifiably placed on the system
Survivability – deals with the recovery of the system after massive failure.
Accountability -- actions affecting security must be traceable
to the responsible party. For this,
Audit information must be kept and protected,
Access control is needed.
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9. Basic Components Threats – potential violations of security
Attacks – violations
Attackers – those who execute the violations
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10. Threats Disclosure or unauthorized access
Deception or acceptance of falsified data
Disruption or interruption or prevention
Usurpation or unauthorized control
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11. More threats Snooping (unauthorized interception)
Modification or alteration
Active wiretapping
Man-in-the-middle attacks
Masquerading or spoofing
Repudiation of origin
Denial of receipt
Delay
Denial of Service
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12. Policy and Mechanisms
A security policy is a statement of what is / is not allowed.
A security mechanism is a method or tool that enforces a security policy.
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13. Goals of Computer Security
Security is about protecting assets.
This involves:
Prevention
Detection
Recovery (reaction / restore assets)
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14. Assumptions of trust P be the set of all possible states of a system
Let
P be the set of all possible states of a system
Q be the set of secure states
A mechanism is secure if P ≤ Q
A mechanism is precise if P = Q
A mechanism is broad if there are states in P which
are not in Q
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15. Assurance Trust cannot be quantified precisely.
System specifications design and implementation can
provide a basis for how much one can trust a system.
This is called assurance.
A system is said to satisfy a specification if the specification correctly states how the system will function.
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16. Assurance - Specifications
A specification is a statement of the desired functioning of a system.
It can be highly mathematical using any of several languages for that purpose.
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17. Assurance – Design/Implementation
A design of a system translates the specifications into components that will implement them.
Given a design the implementation creates a system that satisfies the design.
A program is correct if its implementation performs as specified.
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18. Assurance – Testing
Proofs of correctness require that each line of source code be checked for mathematical correctness.
Because formal proofs of correctness are time consuming, a posteriori verification techniques known as testing have become widespread.
Testing techniques are considerably simpler than formal methods, but do not provide the same degree of assurance: their value is in eliminating common sources of error and forcing designers to define precisely what the system is supposed to do.
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19. Operational issues Operational issues Cost-benefit analysis
Example: a database with salary info, which is used by a second system to print pay checks
Risk analysis
Environmental dependence
Time dependence
Remote risk
Laws and customs
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20. Fundamental Dilemma Functionality or Assurance
Security mechanisms need additional computational
Security policies interfere with working patterns, and can be very inconvenient.
Managing security requires additional effort and costs.
Ideally there should be a tradeoff.
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21. Laws and Customs Export controls Laws of multiple jurisdiction
Human issues
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22. Human issues Organizational problems (who is responsible for what)
People problems (outsiders/insiders)
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23. Tying it all together: how ????
Threats
Policy
Specification
Design
Implementation
Operation & Maintenance
The security life cycle
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24. Computer Security -- Summary
How to achieve Computer Security:
Security principles/concepts: explore general principles/concepts that can be used as a guide to design secure information processing systems.
Security mechanisms: explore some of the security mechanisms that can be used to secure information processing systems.
Physical/Organizational security: consider physical & organizational security measures
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25. Computer Security
Even at this general level there is disagreement on the precise definitions of some of the required security aspects.
References:
Orange book – US Dept of Defense, Trusted Computer System Evaluation Criteria.
ITSEC – European Trusted Computer System Product Criteria.
CTCPEC – Canadian Trusted Computer System Product Criteria
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