Security Services provided by (X.800)

The OSI security architecture is useful to managers as a way of organizing the task of providing security. Furthermore, because this architecture was developed as an international standard, computer and communications vendors have developed security features for their products and services that relate to this structured definition of services and mechanisms.

• 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

The role of a security service

Consider the role of a security service, and what may be required.

• 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

Note both similarities and differences with traditional paper documents, which for example:

  have signatures & dates;

  need protection from disclosure, tampering, or destruction;

  may be notarized or witnessed;

  may be recorded or licensed

Also have a couple of definition of “security services” from relevant standards.

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”

Passive Attacks

Have “passive attacks” which attempt to learn or make use of information from the system but does not affect system resources.

passive attacks

By eavesdropping on, or monitoring of, transmissions to:

+ obtain message contents (as shown above in Stallings Figure 1.3a), or

+ monitor traffic flows

Are difficult to detect because they do not involve any alteration of the data.

• 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. Two types of passive attacks are release of message contents and traffic analysis.
• Passive attacks are very difficult to detect because they do not involve any alteration of the data. Typically, the message traffic is sent and received in an apparently normal fashion and neither the sender nor receiver is aware that a third party has read the messages or observed the traffic pattern. However, it is feasible to prevent the success of these attacks, usually by means of encryption. Thus, the emphasis in dealing with passive attacks is on prevention rather than detection.

Active Attacks

Active Attacks:Also have “active attacks” which attempt to alter system resources or affect their operation.

By modification of data stream to:
+ masquerade of one entity as some other
+ replay previous messages (as shown above in Stallings Figure 1.4b)
+ modify messages in transit
+ denial of service

Active attacks present the opposite characteristics of passive attacks. Whereas passive attacks are difficult to detect, measures are available to prevent their success. On the other hand, it is quite difficult to prevent active attacks absolutely, because of the wide variety of potential physical,software,and network vulnerabilities. Instead, the goal is to detect active attacks and to recover from any disruption or delays caused by them.

• 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.

Security Attack: Expand on definition and use of “security attack”,

Security Attacks:

• any action that compromises the security of information owned by an organization
• information security is about how to prevent attacks, or failing that, to detect attacks on information-based systems
• often threat & attack used to mean same thing
• have a wide range of attacks
• can focus of generic types of attacks
• passive
• active

3 aspects of information security

consider 3 aspects of information security:

• security attack
• security mechanism
• security service

 The OSI security architecture focuses on security attacks,mechanisms,and services. These can be defined briefly as follows:

• Security attack: Any action that compromises the security of information owned by an organization.

• Security mechanism: A process (or a device incorporating such a process) that is designed to detect, prevent,or recover from a security attack.

• Security service: 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 security attacks, and they make use of one or more security mechanisms to provide the service.

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

To assess effectively the security needs of an organization and to evaluate and choose various security products and policies, the manager responsible for security needs some systematic way of defining the requirements for security and characterizing the approaches to satisfying those requirements. This is difficult enough in a centralized data processing environment; with the use of local and wide area networks,the problems are compounded. ITU-T Recommendation X.800, Security Architecture for OSI, defines such a systematic approach. The OSI security architecture is useful to managers as a way of organizing the task of providing security.