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Computer Security Introduction

Computer Security Introduction

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Computer Security Introduction

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  1. Computer SecurityIntroduction

  2. Introduction What is the goal of Computer Security? A first definition: To prevent or detect unauthorized actions by users of the system.

  3. Introduction How do we 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)

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

  5. Computer Security • Confidentiality: prevent unauthorized disclosure of information. • Integrity: prevent unauthorized modification of information. • Availability: prevent unauthorized withholding of information. Additionally: Authenticity, accountability, reliability, safety, dependability, survivability . . .

  6. Computer Security Even at this general level there is disagreement on the precise definitions of some of the required security aspects. References: • TCSEC or 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

  7. 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.

  8. Integrity “Making sure that everything is as it is supposed to be.” For Computer Security this means: Preventing unauthorized writing or modifications.

  9. 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.

  10. Relationship between Confidentiality Integrity and Availability Confidentiality Integrity Secure Availability

  11. Accountability Actions affecting security must be traceable to the responsible party. For this, • Audit information must be kept and protected, • Access control is needed.

  12. Other security requirements • Reliability – deals with accidental damage, • Safety – deals with the impact of the environment on system failure • Dependability – reliance can be justifiably placed on the system • Survivability – deals with the recovery of the system after massive failure.

  13. Computer Security If I must give a definition…. (again) Computer Security deals with the prevention and detection of unauthorized actions by users of the System.

  14. Fundamental dilemma of Computer Security Functionality or Assurance: which one? • Security mechanisms need additional computational resources. • Security policies interfere with working patterns, and can be very inconvenient. • Managing security requires additional effort and costs. • Ideally there should be a tradeoff.

  15. Principles of Computer Security-- fundamental design parameters Application Software | | User ---------------------------|--------------------Resource (subject) | (object) | Hardware The dimensions of Computer Security

  16. Principles of Computer Security Integrity = compliance with a given set of rules. Rules: • Internal consistency of data items • Authorized operations on data items • Access control

  17. 1st Design decision Should protection focus on data, operations or users?

  18. Layers of an IT system • Application – users run application programs tailored to meet specific requirements • Services – application programs make use of services provided by a software packages like a Database Management System (DBMS) or an Object Reference Broker (ORB). • OS – The software packages run on top of the OS which controls access to resources • OS kernel – the OS may have a kernel that mediates every access to the processor or memory • Hardware – (processor & memory) physically stores and manipulates data.

  19. 2nd Design decision In which layer should security be placed?

  20. The onion model of protection mechanisms Application Services OS OS Kernel Hardware

  21. Complexity vs Assurance 3rd Design decision Should security focus on simplicity or security?

  22. Centralized vs Decentralized 4th Design decision Should security control tasks be given to a central entity of left to individual components?

  23. The layer below Physical and organizational security mechanisms define a security perimeter or boundary. Attackers may try to bypass this boundary. Computer Security Physical and organizational security measures protection boundary

  24. The layer below Access to the layer below is controlled through physical and organizational security measures. • Parts of the system that can malfunction without compromising the protection mechanisms lie beyond the perimeter. • Parts that can be used to disable the protection mechanisms lie within the perimeter.

  25. 5th Design decision How to prevent the attacker from accessing the layer below the protection boundary?

  26. Vulnerabilities • Hardware: Interruption (DOS), Modification, Interception (Theft), Fabrication (Substitution) • Software: Interruption (Deletion), Modification, Interception, Fabrication • Data: Interruption (Loss), Modification, Interception, Fabrication

  27. Hardware Hardware is more visible, so it is more easy to add/remove/change devices, intercept traffic, flood with traffic and generally control their functionality. Attacks: physical damage

  28. Software • Interruption (Deletion):surprisingly easy! • Modification: • Logic bombs –failure when certain conditions are met) • Trojan horses –a program that overtly does one thing while covertly does another • Viruses –a specific Trojan horse that can be used to spread its “infection”. • Trapdoors –a program that has a specific entry point • Information leaks in programs –code that makes information accessible to unauthorized users • Interception (Theft): unauthorized copying

  29. Data Hardware security is usually the concern of a relatively small number of staff. Software extends to programmers and analysts who create an modify programs. However data can be readily interpreted by the general public. Because of its visibility data attacks are much more widespread.

  30. Data • Data Confidentiality: wiretapping, planting bugs, sifting though trash receptacles, monitoring electromagnetic radiation, bribing, inferring, requesting … • Data Integrity: a higher level of sophistication is needed. • Salami attacks –shave off a little from many accounts to form a valuable result • Replay attacks

  31. Computer Criminals • Amateurs • Normal people who observe a weakness in a security system • Disgruntled over some negative work situation • Have committed most of computer crimes to date • Crackers • Often high school or university students: cracking is seen as the ultimate victimless crime • Attack for curiosity, self-satisfaction and personal gain • No common profile or motivation

  32. Computer Criminals • Career criminals • Understand the targets of computer crime • Usually begin as computer professionals who later engage in computer crime finding the prospects and payoff good. • Electronic spies and information brokers who recognize • That trading in companies secrets can be lucrative.