Chapter 1 Network security overview

Introduction Security concepts OSI security architecture o Security attacks, o Security Services o Security Mechanisms Models for network (access) security Network security terminologie

 Models for network (access) security

 Network security terminologies

 Changes in information security

OS Security

Network Security

 Computer Security: The protection an information system

in order to attain the applicable objectives of preserving of

information system resources: (CIA Triad)

o Integrity: Prevents unauthorized modification of S&I

o Availability: Prevents disruption of service and productivity

o Confidentiality: Prevents unauthorized disclosure

of systems and information

(includes hardware, software,

firmware, information/ data,

o Privacy: all individual information may be collected and stored and by

whom and to whom that information may be disclosed

 Integrity

o Data integrity: are changed only in a specified and authorized manner

o System integrity: System performs its intended function in an

undamaged manner, avoid to unauthorized handling of the system

 Availability

o Assures that systems work promptly and service is not denied to

authorized users

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Authentication

o Verifying that users are who

they say they are and that each

input arriving at the system

came from a trusted source

Accountability

(nonrepudiation)

o The security goal that

generates the requirement for

actions of an entity to be traced

uniquely to that entity

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 Threat

o A potential for violation of security, it exists and could breach

security and cause harm That is, a threat is a possible danger

that might exploit a vulnerability

 Attack

o An assault (attack) on system security that derives from an

intelligent threat; that is, an intelligent act evade security services

and violate the security policy of a system

 Vulnerability

o A way by which loss can happen

Security attack

Security service

Security mechanism

 ITU-T3 Recommendation X.800,

Security Architecture for OSI.

 The OSI security architecture:

 defines a systematic approach

 is useful to managers in organizing the

task of providing security

 Security attack:

o Any action that compromises the security of information owned

by an organization

 Security mechanism:

o A process (or a device incorporating such a process) that is

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

 Security service:

o A processing or communication service that enhances the

security of the data processing systems and the information

transfers of an organization The services are intended to

counter (cope) security attacks, and they make use of one or

more security mechanisms to provide the service

 A means of classifying security

attacks, used both in RFC 4949

o A passive attack attempts to

learn or make use of

information from the system

but does not affect system

resources

o An active attack attempts to

alter system resources or affect

their operation

 Passive attacks are in the nature of eavesdropping on,

or monitoring of, transmissions.

 The goal of the opponent is to obtain information that is

being transmitted (namespace, IP range, employee, phone numbers…)

 Passive attacks are very difficult to detect, because they

do not involve any alteration of the data

Passive Attack

Release of Message Contents (Interception)

Traffic Analysis

Meet me at Cinemax

determine the location and

identity of communicating

hosts and could observe the

frequency and length of

messages being exchanged

related goals?

 Involve some modification of the data stream or the

creation of a false stream

 Difficult to prevent because of the wide variety of

potential physical, software, and network vulnerabilities

 Goal is to detect attacks and to recover from any

disruption or delays caused by them

Active Attack

Replay Modification

Denial of Service (Interuption)

Masquerade (Fabrication)

27/08/2017 19

Transfer Rs.1000

to Darth

Transfer Rs.1000 to Darth.

• Involves the passive capture of a

data unit and its subsequent

Transfer Rs.10,000

to Darth

• Some portion of a legitimate

message is altered, or messages

are delayed or reordered to

produce an unauthorized effect

related goals?

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• Prevents or inhibits the

normal use or management of

27/08/2017 OSI 23

 The protection of transmitted data from passive

attacks

o Broadest service protects all user data transmitted

between two users over a period of time

o Narrower forms of service includes the protection of a

single message or even specific fields within a message

o This requires that an attacker not be able to observe the

source and destination, frequency, length, or other

characteristics of the traffic on a communications facility

achieve confidentiality

 Can apply to a stream of messages, a single message,

or selected fields within a message

 Connection-oriented integrity service, one that deals with

a stream of messages, assures that messages are

received as sent with no duplication, insertion,

modification, reordering, or replays

 A connectionless integrity service, one that deals

with individual messages - provides protection against

message modification only

 assuring that a communication is accurate

o A single message: assures the recipient that the message is

from the source that it claims to be from

o An ongoing interaction: assures the 2 entities are accurate and

there is not a 3rd party can masquerade as 1 of the 2 legitimate

parties

 2 specific authentication services are defined in X.800:

o Peer entity authentication: Provides for the corroboration

(verification) of the identity of a peer entity in a system

o Data origin authentication: Provides for the corroboration of the

source of a data unit

Quiz: An attacker correctly guesses Alice’s passw ord and logins in as her Is

this a case of

 False positive

 True positive

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Something the individual knows Something the individual process

Something the individual is (Static biometrics)

Something the individual does (Dynam ic biom etric)

PasswordPIN,Answer

Smart card Physical keyToken

fingerprint retina, Faceiris

Voice,HandwritingTyping rhythm

 GOTPass: users employ “images and a one-time

numerical code” in order to secure password.

o usingpatterns and images instead of letters and numbers

o the generated digits random code

Guessing the password for a given user allows impersonation

Impersonating a real login program

Keylogging to steal a password

Four basic techniques are in use:

• User education

• Computer-generated passwords

• Reactive password checking

• Complex password policy

Do not store passwords, but store something that is derived from

them

oUse a one-way hash function and store the result

oThe password file is readable only for root/admin

1 If we do not have a trusted path between a user and the system,

what problem may occur Check the correct answer(s):

User is not able to log into the system

User may provide the password to a malicious program

2 In the past, hashed passwords were stored in a publicly readable file

/etc/passwd Why were shadow password files addedinstead of

making/etc/passwd file readable only to privileged users?

Shadow files are more efficient to access

There is other public information in /etc/passwd file that various

utilities need

1 The hash function used for computing hashed password values

should meet the following requirements.Check the correct answer(s):

Provide more efficient storage of password related information

Its inverse should be very hard to compute

Produce different hashed values for distinct passwords

2 How many unique four digits PINs are possible? Check the correct answer:

1,000

100,000

10,000

1,000,000

 Prevents either sender or receiver from denying a

 To make these assurances, the content must be digitally

signed by the content creator,

 Using a signature that satisfies the following criteria:

o The digital signature is valid

o The certificate associated with the digital signature is current (not

expired)

o The signing person or organization, known as the publisher, is

trusted

o The certificate associated with the digital signature is issued to

the signing publisher by a reputable certificate authority (CA)

 The ability to limit and control the access to host

systems and applications via communications links

o each entity trying to gain access must first be identified, or

authenticated

 ACL is used by many OS to determine whether

users are authorized to conduct different actions

o the mandatory access control (MAC): computer system

o the discretionary access control (DAC): users

o the role-based access control (RBAC): MAC (in special)

 The Bell-LaPadula Model: certain level of access

 BRAC Model:

the system decides

exactly which users are

- RBAC3 includes RBAC0 plus the

added functionality of both RBAC1

and RBAC2

- An RBAC0 system contains the

four types of entities (the minimum

functionality for an RBAC system):

• User: An individuals

• Role: A named job function

• Permission: mode of access

• Session: : A mapping between

a user and an activated subset of

the set of roles to which the user is

assigned

 The mechanisms are divided into those that are implemented

in a specific protocol layer,

o TCP

o Application

security attack

security mechanisms in use:

o cryptographic techniques

algorithms to transform data E(M,K)

assure the integrity of a dataprove the data source ensure the identity of an entityThe insertion of bits into gaps in data stream to prevent traffic analysisEnable selection/ change of particular secure routes for dataUse a trusted third party to assure certain properties of a data exchangeenforce access rights to resources

Detection of security-relevant events.

an independent review and examination of system records and activities

General

Trusted Functionality

Security Label

Event Detection

Security Audit Trail

Security Recovery

Deals with requests from mechanisms -> takes recovery actions

 A security-related transformation:

o encryption of the message: opponent is unreadable,

o addition of a code: verify the identity of the sender

 Some secret information:

o shared by the two principals and, opponent is unknown

o ex, encryption key used in conjunction with the transformation

 A trusted third party:

o achieve secure transmission ex, distributing the secret

information to the two principals while keeping it from any

opponent

o adjudicate disputes (disagreements) between the two principals

concerning the authenticity of a message transmission

 Using this model requires us to:

o design a suitable algorithm for the security transformation

o generate the secret information (keys) used by the algorithm

o develop methods to distribute and share the secret information

o specify a protocol enabling the principals to use the

transformation and secret information for a security service

 Protect an information system from unwanted access.

o Hacker: with no harmful intent, simply gets satisfaction from

breaking and entering a computer system

o The intruder can be a displeased employee who wishes to do

damage or a criminal who seeks to exploit computer assets for

financial gain

 Using this model requires us to:

o Select appropriate gatekeeper functions to identify users

o Implement security controls to ensure only authorized users

access designated information or resources

 Note that model does not include:

o monitoring of system for successful penetration

o monitoring of authorized users for misuse

o audit logging for forensic uses, etc

 Attack- an act that is an intentional or unintentional attempt to cause damage

or compromise to the information and/or the systems that support it

 Threats - a category of objects, persons, or other entities that represents a

potential danger to an asset

 Threat Agent-a specific instance or component of a more general threat

 Vulnerability-weaknesses or faults in a system or protection mechanism that

expose information to attack or damage

 Hacking-Good: to use computers or systems for enjoyment; Bad: to illegally

gain access to a computer or system

 Risk-the probability that threat will exploit a vulnerability with a harmful result

 Subject -an active entity that interacts with an information system and causes

information to move through the system for a specific end purpose

 Object - a passive entity in the information system that receives or contains

information

54

 Access- a subject or object’s ability to use, manipulate, modify, or affect

another subject or object

 Asset- the organizational resource that is being protected

 Control, Safeguard or Countermeasure- security mechanisms, policies or

procedures that can successfully counter attacks, reduce risk, resolve

vulnerabilities, and otherwise improve the security within an organization

 Exploit– to take advantage of weaknesses or vulnerability in a system

 Exposure- a single instance of being open to damage

 Security Blueprint - the plan for the implementation of new security

measures in the organization

 Security Model-a collection of specific security rules that represents the

implementation of a security policy

 Security Posture or Security Profile-a general label for the combination of

all policy, procedures, technology, and programs that make up the total

security effort currently in place

 Draw a matrix similar to Table 1.4 that shows the

relationship between security services and attacks.

 Draw a matrix similar to Table 1.4 that shows the

relationship between security mechanisms and attacks

 William Stallings-Network Security Essentials_

Applications and Standards, 4th Edition-Prentice Hall

2011

 Cryptography and Network Security, Principles

and Practice, William Stallings, Prentice Hall,

Sixth Edition, 2014