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 on 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. 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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14. 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.
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15. Goals of Computer Security
Security is about protecting assets.
This involves:
Prevention
Detection
Reaction (recover/restore assets)
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16. Computer Security 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 (policies)
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17. 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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18. 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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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
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20. Laws and Customs Export controls Laws of multiple jurisdiction
Human issues
Organizational problems (who is responsible for what)
People problems (outsiders/insiders)
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21. Tying it all together: how ????
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