Computer Security Introduction 2/24/2019
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). 2/24/2019
Basic Components Additionally: Authenticity, accountability, reliability, safety, dependability, survivability . . . 2/24/2019
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. 2/24/2019
Integrity “Making sure that everything is as it is supposed to be.” For Computer Security this means: Preventing unauthorized writing or modifications. 2/24/2019
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. 2/24/2019
Relationship between Confidentiality Integrity and Availability Secure Availability 2/24/2019
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. 2/24/2019
Basic Components Threats – potential violations of security Attacks – violations Attackers – those who execute the violations 2/24/2019
Threats Disclosure or unauthorized access Deception or acceptance of falsified data Disruption or interruption or prevention Usurpation or unauthorized control 2/24/2019
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 2/24/2019
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. 2/24/2019
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 2/24/2019
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. 2/24/2019
Goals of Computer Security Security is about protecting assets. This involves: Prevention Detection Reaction (recover/restore assets) 2/24/2019
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) 2/24/2019
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 2/24/2019
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. 2/24/2019
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 2/24/2019
Laws and Customs Export controls Laws of multiple jurisdiction Human issues Organizational problems (who is responsible for what) People problems (outsiders/insiders) 2/24/2019
Tying it all together: how ???? 2/24/2019