Computer Security Introduction

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Computer SecurityIntroduction
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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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Basic Components

• Additionally
• Authenticity, accountability, reliability,
  safety,
• dependability, survivability . . .

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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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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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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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Relationship between Confidentiality Integrity
and Availability

• Confidentiality

Integrity
Secure
Availability
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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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Basic Components

• Threats potential violations of security
• Attacks violations
• Attackers those who execute the violations

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Threats

• Disclosure or unauthorized access
• Deception or acceptance of falsified data
• Disruption or interruption or prevention
• Usurpation or unauthorized control

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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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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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Assumptions of trust

• 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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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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Goals of Computer Security

• Security is about protecting assets.
• This involves
• Prevention
• Detection
• Reaction (recover/restore assets)

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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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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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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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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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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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Tying it all together how ????