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Computer and Data Security - Introduction

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What is 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) is called Computer Security.

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What is Computer Security? For some Computer Security is controlling access to

hardware, software and data of a computerized system. A large measure of computer security is simply keeping the

computer system's information secure. In broader terms, computer security can be thought of as

the protection of the computer and its resources against accidental or intentional disclosure of confidential data, unlawful modification of data or programs, the destruction of data, software or hardware.

Computer security also includes the denial of use of one’s computer facilities for criminal activities including computer related fraud and blackmail.

Finally, computer security involves the elimination of weaknesses or vulnerabilities that might be exploited to cause loss or harm.

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The Need for Computer Security

Why the need for Computer Security?The value of computer assets and services

What is the new IT environment?Networks and distributed applications/servicesElectronic Commerce (E-commerce, E-business)

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The Value of Computer Assets and Services

Most companies use electronic information extensively to support their daily business processes.

Data is stored on customers, products, contracts, financial results, accounting etc.

If this electronic information were to become available to competitors or to become corrupted, false or disappear, what would happen? What would the consequences be? Could the business still function?

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Network Security Issues “The network is the computer” Proliferation of networks has increased security risks

much more. Sharing of resources increases complexity of system. Unknown perimeter (linked networks), unknown path. Many points of attack. Computer security has to find answers to network

security problems. Hence today the field is called Computer and Network

Security.

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Is there a Security Problem in Computing?

Computer fraud in the U.S. alone exceeds $3 billion each year.

Less than 1% of all computer fraud cases are detectedover 90% of all computer crime goes unreported.

“Although no one is sure how much is lost to EFT crime annually, the consensus is that the losses run in the billions of dollars. Yet few in the financial community are paying any heed.”

Average computer bank theft amounts to $1.5 million.

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Computer Crimes ... Over 25% of all Fortune 500 corporations have been

victimized by computer crime with an average loss of $2-10 million.

Total estimated losses due to computer crime range from $300 million to $500 billion per year.

Computer-related crime has been escalating at a dramatic rate.

Computer crimes continue to grow and plague companies.

Computer crime is almost inevitable in any organization unless adequate protections are put in place.

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Data From Real World The following figures are included (source:

Datapro Research) as example, to give an idea what is going on in the real world. Common Causes of damage: Human Error 52%, Dishonest

people 10%, Technical Sabotage 10%, Fire 15%, Water 10% and Terrorism 3%.

Who causes damage? Current employees 81%, Outsiders 13%, Former employees 6%.

Types of computer crime: Money theft 44%, Damage of software 16%, Theft of information 16%, Alteration of data 12%, Theft of services 10%, Trespass 2%.

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Computer Viruses 53% of BYTE readers have suffered losses of

data that cost an average of $14,000 per occurrence.

There are over 3000 viruses with new ones developed daily.

A survey of over 600 companies and government agencies in the U.S. and Canada shows that 63% found at least one virus on their PCs last year.

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Natural Disasters – Another Dimension

Millions of dollars of damage resulted from the 1989 San Francisco earthquake.

The fire at Subang International Airport knocked out the computers controlling the flight display system. A post office near the Computer Room was also affected by the soot which decommissioned the post office counter terminals. According to the caretaker, the computers were not burnt but crashed because soot entered the hard disks.

Fire, Earthquakes, Floods, Electrical hazards, etc. How to prevent?

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Negligence - The Human Factor

Over 85% of the destruction of valuable computer data involves inadvertent acts.

How to prevent?Proper user trainingIdiot proofing

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Computer Security Requirements

Secrecy Integrity Availability Authenticity Non-repudiation Access control

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Secrecy (Confidentiality) Secrecy requires that the information in a

computer system only be accessible for reading by authorized parties.

This type of access includes:PrintingDisplayingOther forms of disclosure, including simply

revealing the existing of an object

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Integrity Integrity requires that the computer system

asset can be modified only by authorized parties.

Modification includes:WritingChangingChanging statusDeleting and Creating

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More About Integrity Integrity: In lay usage, information has integrity when it is timely,

accurate, complete, and consistent. However, computers are unable to provide or protect all of these qualities. Therefore, in the computer security field, integrity is often discussed more narrowly as having two data integrity and system integrity.

“Data integrity is a requirement that information and programs are changed only in a specified and authorized manner.”

System integrity is a requirement that a system “performs its intended function in an unimpaired manner, free from deliberate or inadvertent unauthorized manipulation of the system.”

The definition of integrity has been, and continues to be, the subject of much debate among computer security experts.

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Availability Availability requires that computer system

assets are available to authorized parties. Availability is a requirement intended to assure

that systems work promptly and service is not denied to authorized users.

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Security of Data

Data

Confidentiality

Data

Integrity

Data

Availability

Secure Data

Data

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Authenticity Authenticity means that parties in a information

services can ascertain the identity of parties trying to access information services.

Also means that the origin of the message is certain.

Therefore two types:Principal AuthenticationMessage Authentication

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Non-repudiation Originator of communications can’t deny it

later. Without non-repudiation you could place an

order for 1 million dollars of equipment online and then simply deny it later.

Or you could send an email inviting a friend to the dinner and then disclaim it later.

Non-repudiation associates the identity of the originator with the transaction in a non-deniable way.

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Access Control Unauthorized users are kept out of the system. Unauthorized users are kept out of places on

the system/disk. Typically makes use of Directories or Access

Control Lists (ACLs) or Access Control Matrix Objects: Resources that need to be protected Subjects: Entities that need access to resources Rights: Permissions Each entry is a triple <subject, object, rights>

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Access Control Matrix

OBJECT 1 OBJECT 2 OBJECT 3 OBJECT 4

SUBJECT 1 ORW ORW R X

SUBJECT 2 R RW R R

SUBJECT 3 X X ORW ORW

SUBJECT 4 R R R RW

SUBJECT N X R R X

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Multiple Access Controls

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Security Requirements are often Combined

For example: User authentication

used for access authorization control purposes in confidentiality.

Non-repudiation is combined with authentication.

Confidentiality

AvailabilityIntegrity

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Type of Attacks/Threats in Computer Systems

A threat is a danger which could affect the security (confidentiality, integrity, availability) of assets, leading to a potential loss or damage.

Interruption Interception Modification Fabrication

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Type of Attacks in Computer Systems

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Normal Flow of Information

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Interruption An asset of the system is destroyed or becomes

unavailable or unusable. This is an attack on the availability.

Examples include destruction of a piece of hardware, such as a hard disk, the cutting of a communication link, or the disabling of the file management system.

DOS - Denial of Service Attacks have become very well known.

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Interruption

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Interception Information disclosure/information leakage An unauthorized party gains access to an asset. This is an attack on confidentiality. The unauthorized party could be a person, a

program, or a computer. Examples include:

wiretapping to capture data in a networkthe illicit copying of files or programs

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Interception

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Modification Modification is integrity violation. An unauthorized party not only gains access to

but tampers with an asset. This is an attack on the integrity. Examples include changing values in a data

file, altering a program so that it performs differently, and modifying the content of a message being transmitted in a network.

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Modification

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Fabrication An unauthorized party inserts counterfeit

objects into the system. This is an attack on the authenticity.

Examples include the insertion of spurious messages in a network or the addition of records to a file.

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Fabrication

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Classification of Attacks Computer Security attacks can be classified

into two broad categories:Passive Attacks can only observe communications

or data.Active Attacks can actively modify

communications or data. Often difficult to perform, but very powerful. Examples include Mail forgery/modification TCP/IP spoofing/session hijacking

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Passive Attacks and Active Attacks

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Passive Attacks and Active Attacks

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Passive Attacks Eavesdropping on or monitoring of

transmission. The goal of the opponent is to obtain

information that is being transmitted. Two types:

Release-of-message contentsTraffic Analysis

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Release-of-message Contents

Opponent finds out the contents or the actual messages being transmitted.

How to protect?EncryptionSteganography

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Traffic Analysis More subtle than release-of-message contents. Messages may be kept secret by masking or

encryption but … The opponent figures out information being

carried by the messages based on the frequency and timings of the message.

How to protect?Data/Message PaddingFiller Sequences

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Passive Attacks Problems Difficult to detect because there is no

modification of data. Protection approach should be based on

prevention rather than detection.

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Active Attacks Active attacks involve some sort of

modification of the data stream or the creation of a false stream.

Four sub-categories:MasqueradeReplayModification of MessagesDenial of service

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Masquerade An entity pretends to be another. For the purpose of doing some other form of

attack. Example a system claims its IP address to be

what it is not, IP spoofing. How to protect?

Principal/Entity Authentication

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Replay First passive capture of data and then its

retransmission to produce an unauthorized effect.

Could be disastrous in case of critical messages such as authentication sequences, even if the password were encrypted.

How to protect?Time stampsSequence Numbers

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Modification of Messages Some portion of a legitimate message is altered

or messages are delayed or reordered to produce an unauthorized effect.

How to protect?Message Authentication CodesChaining

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Denial of Service - DOS Prevents the normal use or management of

communication facilities. Such attacks have become very common on the

Internet especially against web servers. On the Internet remotely located hackers can

crash the TCP/IP software by exploiting known vulnerabilities in various implementations.

One has to constantly look out for software updates and security patches to protect against these attacks.

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Problems with Active Attacks

Easy to detect but difficult to prevent. Efforts are directed to quickly recover from

disruption or delays. Good thing is that detection will have a

deterrent effect.

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How Threats Affect Computer Systems

HARDWARE

SOFTWARE

DATA

Interception (Theft)

Interruption (Denial of Service)

Interception (Eavesdropping)

Interruption (Loss)

Interception (Theft)

Interruption (Deletion)

Modification (Malicious Code)

FabricationModification

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A Model for Network Security

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Security Protocols A protocol is a series of steps, involving two or more

parties, designed to accomplish a task. Every one involved in a protocol must know the protocol

and all of the steps to follow in advance. Everyone involved in the protocols must agree to follow it. The protocol must be unambiguous; each step must be well

defined and there must be no chance of misunderstanding. The protocol must be complete; there must be a specified

action for every possible situation. It should not be possible to do more or learn more than what

is specified in the protocol.

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The Actors in Security Protocols

Alice First participant in all the protocols Bob Second participant in all the protocols Carol Participant in three- and four-party protocols Dave Participant in four-party protocols Eve Eavesdropper Mallory Malicious active intruder Trent Trusted arbitrator Victor Verifier PeggyProver Walter Warden; he’ll be guarding Alice and Bob in

some protocols

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Security Protocol Types

Arbitrated Protocols Adjudicated Protocols Self Enforcing

Protocols Example Protocols

Key Exchange Protocols

Authentication Protocols

Time stamping Service Digital Cash

Bob

Trent

Alice

(a) Arbitrated Protocol

Bob TrentAlice

(b) Adjudicated Protocol

Evidence Evidence(After the fact)

BobAlice

(c) Self-enforcing Protocol

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Security Protocol Layers

The further down you go, the more transparent it is

The further up you go, the easier it is to deploy

Application

Presentation

Session

Transport

Netw ork

Datalink

Physical

Application

Presentation

Session

Transport

Netw ork

Datalink

Physical

Email - S/M IM E

SSL

IPSec

PPP - ECP

PHYSICAL NETW ORKEncrypting

NICEncrypting

NIC

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Security Services Provided by Security Protocols

Access control: Protects against unauthorized use.

Authentication: Provides assurance of someone's identity.

Confidentiality: Protects against disclosure to unauthorized identities.

Integrity: Protects from unauthorized data alteration.

Non-repudiation: Protects against originator of communications later denying it.

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Security Mechanisms Three basic building blocks are used:

Encryption is used to provide confidentiality, can provide authentication and integrity protection.

Digital signatures are used to provide authentication, integrity protection, and non-repudiation.

Checksums/hash algorithms are used to provide integrity protection, can provide authentication.

One or more security mechanisms are combined to provide a security service/protocol.

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Services, Mechanisms, Algorithms

A typical security protocol provides one or more security services (authentication, secrecy, integrity, etc.)

Services are built from mechanisms. Mechanisms are implemented using algorithms.

SSL

Signatures Encryption Hashing

DSA RSA RSA DES SHA1 MD5

Services (Security Protocols)

Mechanisms

Algorithms

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Security Protocols (Services)

Standards-based Security Protocols Proprietary Security Protocols

SSL IPSec PrivateWire Big Brother

Mechanisms

Encryption Signature Hashing Key Exchange

Algorithms

Symmetric Asymmetric Asymmetric Symmetric

MD-5SHA-1

Diffie-HellmanDESAES

RSAECC

DSARSA

DESMAC

Services, Mechanisms, Algorithms

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Encryption and Security Encryption is a key enabling technology to

implement computer security. But Encryption is to security like bricks are to

buildings. In the next module we will study encryption in

detail.

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Network Access Security Model

Firewalls and Security Gateways are based on this model

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Computer security is based on eight major elements:

1. Computer security should support the mission of the organization.

2. Computer security is an integral element of sound management.

3. Computer security should be cost-effective.4. Computer security responsibilities and accountability

should be made explicit.5. System owners have computer security responsibilities

outside their own organizations.6. Computer security requires a comprehensive and integrated

approach.7. Computer security should be periodically reassessed.8. Computer security is constrained by societal factors.

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Usability and Security

Security

Convenience / Usability

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Determine where on this

line your organization

needs lie

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Typical Security Solutions and Technologies

Physical security Encryption Access control Automatic call back Node authentication Differentiated access

rights Antivirus software Public Key

Infrastructure Firewalls

User authentication Passwords and

passphrases Challenge-response

systems Token or smart cards Exchange of secret

protocol Personal characteristics -

Biometrics