COSC 472 Network Security

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COSC 472 Network Security Annie Lu 1

COSC 472 Network Security

• Instructor: Dr. Enyue (Annie) Lu

– Office hours:

http://faculty.salisbury.edu/~ealu/schedule.htm

– Office room: HS114

– Email: [email protected]

• Course information:

– http://faculty.salisbury.edu/~ealu/COSC472/cosc472.html – MyClasses@SU

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Course overview

• Chapter 1: Introduction

• Part I: Cryptography

• Chapter 2: Symmetric Encryption & Message Confidentiality

• Chapter 3: Public-Key Cryptography & Message Authentication

• Part II –III: Network Security

• Chapter 4: key Distribution & User Authentication

• Chapter 5: Network Access Control and Cloud Security

• Chapter 6. Transport-Level Security

• Chapter 7. Wireless Network Security

• Chapter 8: E-mail Security

• Chapter 9: IP Security

• Part III: System security

• Chapter 10. Malicious Software

• Chapter 11. Intruder

• Chapter 12. Firewalls

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Chapter I: Introduction

• Outline

– What’s network security – Security threats

– Security architecture – Security attacks

– Security services

– Security mechanisms

– Network security models

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COSC 472 Network Security Annie Lu

Chapter 1 – Introduction

The art of war teaches us to rely not on the

likelihood of the enemy's not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position

unassailable.

—The Art of War, Sun Tzu

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Background

• Information Security requirements have changed in recent times

• Traditionally provided by physical and administrative mechanisms

• Computer use requires automated tools to protect files and other stored information

• Use of networks and communications links requires measures to protect data during

transmission

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Security

• Information Security:

– is about how to prevent attacks, or failing that, to detect attacks on information-based systems

• Computer Security:

– generic name for the collection of tools designed to protect data and to thwart hackers

• Network Security:

– measures to protect data during their transmission

• Internet Security:

– measures to protect data during their transmission over a collection of interconnected networks

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Computer Security

• the protection afforded to an automated information system in order to attain the applicable objectives of preserving the

integrity, availability and confidentiality of information system resources (includes

hardware, software, firmware,

information/data, and telecommunications)

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CIA Triad

Data and services

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CIA Triad

• Confidentiality:

– Data confidentiality: confidential information should not be accessible to unauthorized users

– Privacy: individuals control what information related to them

• Integrity:

– Data integrity: data may only be modified through an authorized mechanism

– System integrity: system performs intended function

• Availability: authorized users should be able to access data for legitimate purposes as necessary

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Examples of Security Requirements

• confidentiality – student grades

• integrity – patient information

• availability – authentication service

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Levels of Impact

can define 3 levels of impact from a security breach

Low

Moderate

High

P22: Problem1.4

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Computer Security Challenges

1. not simple

2. must consider potential attacks

3. procedures used counter-intuitive

4. involve algorithms and secret info

5. must decide where to deploy mechanisms

6. battle of wits between attacker / admin

7. not perceived on benefit until fails

8. requires regular monitoring

9. too often an after-thought

10. regarded as impediment to using system

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Computer Security vs. Network Security

• Computer security deals with protecting a single machine

• Network security deals with protecting the communication and all participants in it

– Goal of networking is to enable communication at all times and in all scenarios!

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What Does Network Security Mean?

• I want to talk to Alice. No one should be able to:

– Break into my computer – Attack my computer

– Steal my information

– Use my computer to attack others – Damage my computer or data

– Pretend to be Alice or myself or our computers – Use my resources

– Prevent me from communicating with Alice

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Aim of Course

• our focus is on Internet Security

• which consists of measures to deter, prevent, detect, and correct security

violations that involve the transmission &

storage of information

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Security Trends

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Threats and Attacks

• Threat: a potential for violation of security;

a possible danger that might exploit a vulnerability

• Attack: an assault on system security that derives from an intelligent threat

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What Are the Threats?

• No one should be able to break into my computer

– Hackers

• Break a password or sniff it off the network

• Exploit a vulnerability

– A vulnerability is a bug in the software that creates unexpected computer behavior when exploited, such as enabling access without login, running unauthorized code or crashing the computer.

– An exploit is an input to the buggy program that makes use of the existing vulnerability

• Use social engineering: eg. phishing

• Impersonate someone I trust

– Viruses and worms

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What Are the Threats?

• No one should be able to attack my computer

– Denial-of-service attacks

• A DOS attack aims to disrupt a service by either exploiting a vulnerability or by sending a lot of bogus messages to a

computer offering a service

– Viruses and some worms

• A virus is a self-replicating program that requires user action to activate such as clicking on E-mail, downloading an infected file or inserting an infected floppy, CD, etc ..

• A worm is a self-replicating program that does not require user action to activate. It propagates itself over the network, infects any vulnerable machine it finds and then spreads from it

further.

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What Are the Threats?

• No one should be able to steal my information

– From my computer or from communication – I will use cryptography!

• There are many ways to break ciphers

• There are many ways to divulge partial information (e.g. who do you talk to)

– I would also like to hide who I talk to and when

• I will use anonymization techniques

• Anonymization hinders other security approaches that build models of normal traffic patterns

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What Are the Threats?

• No one should be able to use my machine to attack others

– E-mail viruses – Worms

– Denial-of-service attacks (including reflector attacks)

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What Are the Threats?

• No one should be able to damage my computer or data

– I have to prevent break-ins

– I will also use cryptography to detect tampering – I must replicate data to recover from tampering – Denial-of-service attacks and worms can

sometimes damage computers

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What Are the Threats?

• No one should be able to successfully pretend to be Alice or myself or our computers

– I want to be sure who I am talking to (authentication and digital signatures)

– It is hard to impersonate a computer in two-way communication, such as TCP. But it has been done – Plain IP spoofing seems extremely hard problem to

solve

• IP spoofing means putting a fake IP address in the sender field of IP packets.

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What Are the Threats?

• No one should be able to take up my resources with irrelevant messages

– Denial-of-service attacks

– Spam mail (takes time to read and fills space) – Malicious mail (may contain a virus)

– Viruses and worms

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What Are the Threats?

• No one should be able to prevent me from communicating with Alice

– Alice could be attacked

– Routers could be overloaded or tampered with – DNS servers could be attacked

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OSI Security Architecture

• ITU-T X.800 “Security Architecture for OSI”

• defines a systematic way of defining and providing security requirements

• for us it provides a useful, if abstract, overview of concepts we will study

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Security Architecture

• Security Attack: Any action that

compromises the security of information.

• Security Mechanism: A mechanism that is designed to detect, prevent, or recover from a security attack.

• Security Service: A service that enhances the security of data processing systems and information transfers. A security service

makes use of one or more security mechanisms.

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Passive attack: attempts to learn or make use of information from the system but does not affect system resource.

Active attack: attempts to alter system resources or affect their operation

attack

attack attack

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Passive Attacks

• Release of the message contents: read the contents of the message

• Traffic analysis: observe the pattern of the massage

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Release of the message contents

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Traffic analysis

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Active attacks

• Masquerade: one entity pretends to be a different entity

• Replay: involves the passive capture of a data unit and its subsequent retransmission to produce an

unauthorized effect

• Modification of message: some portion of a

legitimate message is altered, or that messages are delayed or reordered.

• The denial of service: prevents or inhibits the normal use or management of communications facilities

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Masquerade

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Replay

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Modification of message

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The denial of service

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Security Attacks

attack

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Security Attacks

• Interruption: This is an attack on availability

• Interception: This is an attack on confidentiality

• Modification: This is an attack on integrity

• Fabrication: This is an attack on authenticity

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Security Mechanism

• feature designed to detect, prevent, or recover from a security attack

• no single mechanism that will support all services required

• however one particular element underlies many of the security mechanisms in use:

– cryptographic techniques

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Security Mechanisms (X.800)

(P. 15: Table 1.3)

• specific security mechanisms:

– encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarization

• pervasive security mechanisms:

– trusted functionality, security labels, event

detection, security audit trails, security recovery

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Security Service

– enhance security of data processing systems and information transfers of an organization

– intended to counter security attacks

– using one or more security mechanisms

– often replicates functions normally associated with physical documents

• which, for example, have signatures, dates; need

protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed

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Security Services

• X.800:

“a service provided by a protocol layer of

communicating open systems, which ensures adequate security of the systems or of data transfers”

• RFC 2828:

“a processing or communication service provided by a system to give a specific kind of protection to

system resources”

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Security Services

(P. 12: Table 1.2)

• Authentication - assurance that the communicating entity is the one claimed

• Access Control - prevention of the unauthorized use of a resource

• Data Confidentiality –protection of data from unauthorized disclosure

• Data Integrity - assurance that data received is as sent by an authorized entity

• Non-Repudiation - protection against denial by one of the parties in a communication

– Proof that the message was sent by specific party (Nonrepudiation origin)

– Proof that the message was received by specific party (Nonrepudiation destination)

• Availability (permanence, non-erasure) – Denial of Service Attacks

– Virus that deletes files

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Model for Network Security

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Model for Network Security

• using this model requires us to:

1. design a suitable algorithm for the security transformation

2. generate the secret information (keys) used by the algorithm

3. develop methods to distribute and share the secret information

4. specify a protocol enabling the principals to use the transformation and secret information for a security service

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Model for Network Access Security

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Model for Network Access Security

• using this model requires us to:

1. select appropriate gatekeeper functions to identify users

2. implement security controls to ensure only authorised users access designated

information or resources

• trusted computer systems may be useful to help implement this model

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Internet standards and RFCs

• The Internet society

– Internet Architecture Board (IAB)

– Internet Engineering Task Force (IETF) – Internet Engineering Steering Group

(IESG)

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Internet RFC Publication

Process

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Summary

• Definitions of computer, network, internet security

• security concepts:

– confidentiality, integrity, availability

• Security architecture

• security attacks, services, mechanisms

• models for network (access) security