INTRODUCTION TO COMPUTER SECURITY

Dr. Shahriar BijaniShahed University

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SLIDE REFERENCES Matt Bishop, Computer Security: Art and

Science, the author homepage, 2004. Michael E. Whitman, Principles of

Information Security: Chapter 1: Introduction to Information Security, 4/e, 2011.

Chris Clifton, CS 526: Information Security course, Purdue university, 2010.

Patrick Traynor, CS 8803 - Cellular and Mobile Network Security, Georgia Tec, 2012.

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WHAT IS SECURITY?

Security /sɪˈkjʊərɪti/noun the state of being free from danger or threat. synonyms: certainty, safe future, assured

future, safety, reliability, dependability, solidness, soundness

WHAT IS SECURITY? A successful organization should have multiple

layers of security in place: Physical security: to protect the physical items,

objects, or areas of an organization from unauthorized access and misuse.

Personal security: to protect the (group of) authorized individual.

Operations security: to protect the details of a particular operation or series of activities.

Communications security: to protect an organization’s communications media, technology, and content.

Network security: to protect networking components, connections, and contents.

Information security4

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BASIC COMPONENTS An Information System is secure if it supports

CIA:Confidentiality

Keeping data and resources hiddenIntegrity

Data integrity (integrity)Origin integrity (authentication)

Availability Enabling access to data and resources

The CIA triangle

THE HISTORY OF INFORMATION SECURITY

Began immediately following development first mainframes Developed for code-breaking computations During World War II Multiple levels of security were implemented

Physical controls Elementary

Mainly composed of simple document classification

Defending against physical theft, espionage, and sabotage

THE 1960S Original communication by mailing tapes Advanced Research Project Agency (ARPA)

Examined feasibility of networked communications

Larry Roberts developed ARPANET Plan

Link computers Resource sharing Link 17 Computer Research Centers Cost 3.4M $

ARPANET is predecessor to the Internet

THE 1970S AND 80S ARPANET grew in popularity Potential for misuse grew Fundamental problems with ARPANET security

Individual remote sites were not secure from unauthorized users

Vulnerability of password structure and formats No safety procedures for dial-up connections to

ARPANET Non-existent user identification and authorization to

system

THE 1970S AND 80S … Rand Report R-609

Paper that started the study of computer security Information Security as we know it began

Scope of computer security grew from physical security to include: Safety of data Limiting unauthorized access to data Involvement of personnel from multiple levels of an

organization

THE 1990S Networks of computers became more common Need to interconnect networks grew Internet became first demonstration of a global

network of networks Initially based on de-facto standards In early Internet deployments, security was

treated as a low priority

2000 TO PRESENT Millions of computer networks communicate Many of the communication unsecured Ability to secure a computer’s data influenced

by the security of every computer to which it is connected

Growing threat of cyber attacks has increased the need for improved security

CHALLENGES OF COMPUTER SECURITY1. Computer security is not simple2. One must consider potential (unexpected)

attacks3. Must decide where to deploy mechanisms4. Involve algorithms and secret info (keys)5. A battle between attacker / admin6. It is not perceived on benefit until fails7. Requires constant monitoring8. Too often incorporated after the design is complete (not

integral)9. Regarded as a barrier to using system

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KEY INFORMATION SECURITY CONCEPTS

Access Adversary Asset Attack Control, Safeguard, or

Countermeasure Exploit Exposure Hack Loss Nonrepudiation

• Subjects / Objects• Risk• Threat• Vulnerability

RELATIONSHIPS OF SECURITY CONCEPTS

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KEY INFORMATION SECURITY CONCEPTS Computer can be subject or object of an

attackWhen the subject of an attack

An active tool to conduct attackWhen the object of an attack

An entity being attackedSource: Principles of Information Security, 4th Edition

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INFORMATION SECURITY VS. ACCESS

Perfect security is impossibleSecurity is a process Security should be considered balance

between protection and availability Must allow reasonable access, yet

protect against threats

18Source: Principles of Information Security, 4th Edition

INFORMATION SECURITY VS. ACCESS

VULNERABILITIES

19Principles of Information Security, 4/e

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THREATS A threat is a potential violation of security.

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CLASSES OF THREATS Interruption (Disruption)

interruption or prevention of correct operationDOS attack: Denial of Service

Interception / DisclosureUnauthorized access to informationSnooping: the unauthorized interception of

informationModification

An unauthorized party not only gains access to but modify an asset.

Masquerading or spoofing: an impersonation of one entity by another.

FabricationAn unauthorized party inserts fake objects into the

system.

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CLASSES OF THREATS

EXAMPLES OF THREATS

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ADVERSARY An adversary is anyone attempting to bypass the

security infrastructure. The curious and generally inexperienced (e.g.,

script-kiddies) Unintended attackers seeing to understand systems Malicious and terrorist groups Competitors (industrial espionage) Governments

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ATTACK An attack occurs when someone attempts to

exploit a vulnerability Type of attacks

Passive (e.g., eavesdropping) Active (e.g., password guessing, DoS)

A compromise occurs when an attack is successful

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TRUST Trust

The degree to which an entity is expected to behave.

Trust is a particular level of the subjective probability with which an agent assesses that another agent will perform a particular action in a context that affects his actions [Gambetta, 1990]

ReputationExpectation about an entity’s behavior based

on past behavior [Abdul-Rahman, 2000]May be used to determine trust

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TRUST MANAGEMENT Trust Management as a countermeasure:

Trust relationships between peers help establish confidence

Two types of trust management systemsCredential and Policy-basedReputation-based

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SECURITY MODEL A security model is the combination of a trust and threat

models that address the: set of perceived risks The “security requirements” used to develop some cogent and

comprehensive design Every design must have security model LAN network or global information system? Java applet or operating

system? The single biggest mistake seen in use of security is the lack of

a coherent security model

It is very hard to retrofit security (design time) This class is going to talk a lot about security models What are the security concerns (risks)? Threats? Who are our adversaries? Who do we trust and to do what? Systems must be explicit about these things to be secure

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POLICIES AND MECHANISMS

Policy says what is, and is not, allowed This defines “security” for the site/system/etc.

Mechanisms enforce policies Composition of policies

If policies conflict, inconsistencies may create security vulnerabilities

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TRUST AND ASSUMPTIONS

Underlie all aspects of security Policies

Unambiguously partition system states Correctly capture security requirements

Mechanisms Assumed to enforce policy Support mechanisms work correctly

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GOALS OF SECURITY

Prevention(پیشگیری) Prevent attackers from violating security policy

Detection (تشخیص) Detect attackers’ violation of security policy

Recovery (ترمیم) Stop attack, assess and repair damage Continue to function correctly even if attack

succeeds