INSTRUSION DETECTION

SYSTEM ( I D S )

The OSI Security architecture• Security attacks• Security services• Security mechanism

A model for network security

Introduction

The OSI security architecture focuses on security attacks, mechanisms, and services.

Security attack:Any action that compromises the

security of information owned by an organization. Two types of security attacks a) Passive attack b) active attack

The OSI security architecture

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

Two types of passive attacks are release of message contents and traffic analysis.

Passive attack

Passive attack

Active attacks involve some modification of the data stream or the creation of a false stream and can be subdivided into four categories : masquerade , replay, modification of messages, and denial of service.

Active attack

Active attack

Active attack

X.800 defines it is the service provided by protocol layer of communicating open system which ensures adequate security of the systems or of data transfers.

RFC 2828 defines as a communication service that is provided by a system to give a specific kind of protection to system resources;

Security service

Authentication Access control Data confidentiality Data integrity Nonrepudiation

Security services are divided into

five categories

Is a process that is designed to detect, prevent or recover from a security attack.

Encipherment : It uses a mathematical algorithm to transfer the data into a form that can not be read by unauthorized user.

Two types: Reversible encipherment Irreversible encipherment

Security mechanism

Model for Network Security

A security-related transformation on the information to be sent.

Some secret information shared by the two principals and, it is hoped, unknown to the opponent.

Techniques for providing security

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