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An Overview of Computer Security. Outline. Components of computer security Threats Policies and mechanisms The role of trust Assurance Operational Issues Human Issues. Status of security in computing (in early 2000s). In terms of security, computing is very close to the wild west days.

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An overview of computer security

An Overview ofComputer Security

computer security


  • Components of computer security

  • Threats

  • Policies and mechanisms

  • The role of trust

  • Assurance

  • Operational Issues

  • Human Issues

computer security

Status of security in computing in early 2000s
Status of security in computing (in early 2000s)

  • In terms of security, computing is very close to the wild west days.

  • Some computing professionals & managers do not even recognize the value of the resources they use or control.

  • In the event of a computing crime, some companies do not investigate or prosecute.

Has the status changed for the better?

computer security

Characteristics of computer intrusion
Characteristics of Computer Intrusion

  • A computing system: a collection of hardware, software, data, and people that an organization uses to do computing tasks

  • Any piece of the computing system can become the target of a computing crime.

  • The weakest point is the most serious vulnerability.

  • The principles of easiest penetration

computer security

Security breaches terminology
Security Breaches- Terminology

  • Exposure

    • a form of possible loss or harm

  • Vulnerability

    • a weakness in the system

  • Attack

  • Threats

    • Human attacks, natural disasters, errors

  • Control – a protective measure

  • Assets – h/w, s/w, data

computer security

Types of security breaches
Types of Security Breaches

  • Disclosure: unauthorized access to info

    • Snooping

  • Deception: acceptance of false data

    • Modification, spoofing, repudiation of origin, denial of receipt

  • Disruption: prevention of correct operation

    • Modification, man-in-the-middle attack

  • Usurpation: unauthorized control of some part of the system (usurp: take by force or without right)

    • Modification, spoofing, delay, denial of service

computer security

Security components
Security Components

  • Confidentiality: The assets are accessible only by authorized parties.

    • Keeping data and resources hidden

  • Integrity: The assets are modified only by authorized parties, and only in authorized ways.

    • Data integrity (integrity)

    • Origin integrity (authentication)

  • Availability: Assets are accessible to authorized parties.

    • Enabling access to data and resources

computer security

Computing system vulnerabilities
Computing System Vulnerabilities

  • Hardware vulnerabilities

  • Software vulnerabilities

  • Data vulnerabilities

  • Human vulnerabilities ?

computer security

Software vulnerabilities
Software Vulnerabilities

  • Destroyed (deleted) software

  • Stolen (pirated) software

  • Altered (but still run) software

    • Logic bomb

    • Trojan horse

    • Virus

    • Trapdoor

    • Information leaks

computer security

Data security
Data Security

  • The principle of adequate protection

  • Storage of encryption keys

  • Software versus hardware methods

computer security

Other exposed assets
Other Exposed Assets

  • Storage media

  • Networks

  • Access

  • Key people

computer security

People involved in computer crimes
People Involved in Computer Crimes

  • Amateurs

  • Crackers

  • Career Criminals

computer security

Methods of defense
Methods of Defense

  • Encryption

  • Software controls

  • Hardware controls

  • Policies

  • Physical controls

computer security


  • at the heart of all security methods

  • Confidentiality of data

  • Some protocols rely on encryption to ensure availability of resources.

  • Encryption does not solve all computer security problems.

computer security

Software controls
Software controls

  • Internal program controls

  • OS controls

  • Development controls

  • Software controls are usually the 1st aspects of computer security that come to mind.

computer security

Policies and mechanisms
Policies and Mechanisms

  • Policy says what is, and is not, allowed

    • This defines “security” for the site/system/etc.

  • Mechanisms enforce policies

  • Mechanisms can be simple but effective

    • Example: frequent changes of passwords

  • Composition of policies

    • If policies conflict, discrepancies may create security vulnerabilities

  • Legal and ethical controls

    • Gradually evolving and maturing

computer security

Principle of effectiveness
Principle of Effectiveness

  • Controls must be used to be effective.

    • Efficient

      • Time, memory space, human activity, …

    • Easy to use

    • appropriate

computer security

Overlapping controls
Overlapping Controls

  • Several different controls may apply to one potential exposure.

    H/w control + S/w control + Data control

computer security

Goals of security
Goals of Security

  • Prevention

    • Prevent attackers from violating security policy

  • Detection

    • Detect attackers’ violation of security policy

  • Recovery

    • Stop attack, assess and repair damage

    • Continue to function correctly even if attack succeeds

computer security

Trust and assumptions
Trust and Assumptions

  • Underlie all aspects of security

  • Trust and verify vs Verify before trust?

  • Policies

    • Unambiguously partition system states

    • Correctly capture security requirements

  • Mechanisms

    • Assumed to enforce policy

    • Support mechanisms work correctly

computer security

Types of mechanisms
Types of Mechanisms




set of reachable states

set of secure states

computer security


  • Specification

    • Requirements analysis

    • Statement of desired functionality

  • Design

    • How system will meet specification

  • Implementation

    • Programs/systems that carry out design

computer security

Operational issues
Operational Issues

  • Cost-Benefit Analysis

    • Is it cheaper to prevent or to recover?

  • Risk Analysis

    • Should we protect something?

    • How much should we protect this thing?

  • Laws and Customs

    • Are desired security measures illegal?

    • Will people do them?

computer security

Human issues
Human Issues

  • Organizational Problems

    • Power and responsibility

    • Financial benefits

  • People problems

    • Outsiders and insiders

    • Social engineering

“The methods that will most effectively minimize the ability of intruders to compromise information security are comprehensive user training and education. Enacting policies and procedures simply won't suffice. Even with oversight the policies and procedures may not be effective: my access to Motorola, Nokia, ATT, Sun depended upon the willingness of people to bypass policies and procedures that were in place for years before I compromised them successfully.” — Kevin Mitnick

computer security

Tying together
Tying Together







computer security

Key points
Key Points

  • Policy defines security, and mechanisms enforce security

    • Confidentiality

    • Integrity

    • Availability

  • Trust and knowing assumptions

  • Importance of assurance

  • The human factor

computer security