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Introduction to Introduction to Network Network SecuritySecurity

Spring 2011

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OutlineOutline

• Introduction• Attacks, services and mechanisms• Security threats and attacks• Security services• Methods of Defense• A model for Internetwork Security• Internet standards and RFCs

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IntroductionIntroduction GoalInformatio

nSecurity

ComputerSecurity

NetworkSecurity

Automated toolsfor protecting infoon the computer

Measures to protectdata during theirtransmission on the network

Services

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Security TrendsDDoS to DNS2003

BotNet Attack2009

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HackingHacking• Attack using the vulnerability of protocol

– DoS

– Sniffing

– Session Hijacking

– Spoofing

• Malicious code– Virus

– Trojan horse

– Back door

– Worm

John Draper, Phone hacker

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Virus and Worm

• What is Virus?– Self-replicating code

– Inserts itself into other executable code

– Contains a malicious function, called payload (can be empty)

– Native code which infects executable files

– Distribution by Email and File sharing

– Often requires a trigger from a user• e.g. execute infected application

– Virus is often used as a collective term for malware

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Trojan Horse• A destructive program that masquerades as

a benign application. Unlike viruses, Trojan horses do not replicate themselves but they can be just as destructive.– A Trojan horse can be deliberately attached to

otherwise useful software by a cracker, or it can be spread by tricking users into believing that it is a useful program.

• The term comes from the a Greek story of the Trojan War : between Greek and Troy

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Virus and Worm• What is Worm?

– First Internet worm in 1988– Different to a virus

• Stand-alone program• Does not infect an application• Spreads itself through the network automatically• Usually spread much faster than viruses

– Worms often use exploits to propagate• SQL Slammer – MS SQL Server• Slapper - Apache/Mod-SSL• Code Red – MS Internet Information Server

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Attacks, Services and Attacks, Services and MechanismsMechanisms

• 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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Security Threats & AttacksSecurity Threats & Attacks

•Threats• A possible danger that might exploit a

vulnerability given a Circumstance, Capability, action, or event to breach security and cause harm

• Attacks• An assault on system security that

derives from an intelligent threat

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Security ThreatsSecurity Threats

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Security ThreatsSecurity Threats

• Interruption: This is a threat on availability

• Interception: This is a threat on confidentiality

• Modification: This is a threat on integrity

• Fabrication: This is a threat on authenticity

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Security AttacksSecurity Attacks• Passive Attack : Attempts to learn or make use of information from the system, but no affect on

system resources

- Release of message contents- Traffic analysis

• Active Attack : Attempts to data system resources or affect their operations

- Masquerade- Replay- Modification of message- Denial of service : 2003.1.25 Internet

Chaos, 2007.7.7/ 2011.3.3 DDoS Attack

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Release of Message Release of Message ContentsContents

Sensitive or confidential info needs to be prevented from an opponent who will learn the contents of the there transmissions

Internet orother comms

facility

Darth Read contents of

message from Bob to Alice

Bob Alice

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Traffic AnalysisTraffic Analysis

If the contents of msgs are masked or protected by encryption, and opponent might still be able to observe the pattern of msgs,

• such as source and dest of communicating hosts,

• frequency and length of msgs being exchanged.

Internet orother communications

facility

Darth Observe pattern ofmessages from Bobto Alice

Bob Alice

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Masquerade Masquerade

• Taking place when one entity pretends to be a different entity• Enabling an authorized entity with few privileges to obtain extra privileges by impersonating an entity that has those privileges.

Internet orother comms

facility

Darth Read contents

of message from Bob to Alice

Bob Alice

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Replay attackReplay attack

The passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect.

Internet orother comms facility

Darth Capture message fromBob to Alice; laterreplay message to Alice

Bob Alice

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ModificationModification of Message of Message

Some portion of legitimate msg altered, delayed, or reordered to produce an unauthorized effect.

Internet orother comms

facility

Darth Darth modifiesmessage from Bobto Alice

Bob Alice

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DenialDenial of Service of Service

The normal use of communications facilities prevented or inhibited, such as

• Suppressing all msgs directed to a particular dest.

• The disruption of an entire network by disabling the network

• The degradation of performance by overloading it with msgs

An Architecture of DDoS Attack

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Victim

Daemon

Daemon

DaemonDaemon

Daemon

Master

Real Attacker

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Security ServiceSecurity Service

• A service that is provided by a protocol layer of communicating open system and that ensures adequate security of the systems or of data transfer

• Security services implement security policies and are implemented by security mechanisms

• Classification of the services– Authentication - Data Integrity– Access control - Nonrepudiation– Data confidentiality - Availability

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AuthenticationAuthentication• This service is concerned with assuring that a

communication is authentic

• Data origin authentication (in the case of a single message)

– The function of the authentication service is to assure the recipient that the message is from the original source.

– No service on duplication or modification.

• Peer entity authentication (in a connection-oriented transmission i.e TCP)

– At the time of connection initiation, the service assures that the two entities are authentic

– On the way of transmissions, the service assures that the connection is not interfered by a third party to masquerade as one of the entities.

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Access ControlAccess Control

• The prevention of unauthorised use of a resource

• In the context of network security, this service is the ability to limit and control the access to host systems and applications via communications links.

• Each entity must be identified or authenticated then, access rights can be tailored to the individual.

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Data ConfidentialityData Confidentiality

• The protection of transmitted data from passive attacks.

• Types of data confidentiality– Connection confidentiality (all user data on a

connection)– Connectionless confidentiality (all user data in a single

msg.)– Selective field confidentiality (specific fields within a

use data)– Traffic-flow confidentiality (information for traffic flow)

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Data IntegrityData Integrity• To provide the assurance that the received data are

exactly the same as the data transmitted by an authorised entity.

※ no modification, insertion, deletion, or replay

• A connection-oriented / connectionless integrity service

– Connection-oriented : deals with a stream of messages & assures no duplication, alteration, or replays on the messages.

– Connectionless : deals with individual messages & may provide protection on data modification

• Integrity service with / without recovery– The automated recovery mechanism is more

attractive.

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NonrepudiationNonrepudiation

• To prevent either sender or receiver from denying a transmitted message.

– Origin (sender): Proof that the message was sent by the specified party.

– Destination (receiver): Proof that the message was received by the specified party.

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AvailabilityAvailability

• Provides the normal use of a system or system resource

• Addresses the security concerns raised by denial-of-service attack.

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Security MechanismsSecurity Mechanisms

• Specific Security Mechanisms– Implemented in a specific protocol

layer.

• Pervasive Security Mechanisms– Not specific to any particular

protocol layer or security service.

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A Model for Network A Model for Network SecuritySecurity

Sec

ure

Mes

sage

Mes

sage

Trusted third party (e.g., arbiter, distributer of secret information)

Opponent

Secretinformation

Secretinformation

Security-relatedtransformation

Security-relatedtransformation

Informationchannel

Sec

ure

Mes

sage

Mes

sage

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Methods of DefenceMethods of Defence

• Encryption• Software Controls (access limitations

in a data base, in operating system protect each user from other users)

• Hardware Controls (smartcard)• Policies (frequent changes of

passwords)• Physical Controls

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Internet standards and Internet standards and RFCsRFCs

• The Internet society– Internet Architecture Board (IAB)– Internet Engineering Task Force (IETF)– Internet Engineering Steering Group

(IESG)

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Internet RFC Internet RFC Publication ProcessPublication Process

InternetDraft

InternetDraft

ProposedStandard

ProposedStandard

Best currentPractice

Best currentPractice ExperimentalExperimental InformationalInformational

DraftStandard

DraftStandard

InternetStandard

InternetStandard

HistoricHistoric

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Summary

• We deals with – security trends– Security attacks such as passive attacks and active

attacks– Security services such as authentication, access

control, data confidentiality, data integrity, nonrepudiation and availability service

– A model for network security including Opponent, Access Channel, Gatekeeper Function and Information System

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Outline of the Course • This chapter serves as an introduction to the entire course. The

remainder of the book is organized into three parts:• Part One : Provides a concise survey of the cryptographic

algorithms and protocols underlying network security applications, including encryption, hash functions, digital signatures, and key exchange.

• Part Two : Examines the use of cryptographic algorithms and security protocols to provide security over networks and the Internet. Topics covered include user authentication, e-mail, IP security, and Web security.

• Part Three : Deals with security facilities designed to protect a computer system from security threats, including intruders, viruses, and worms. This part also looks at firewall technology.