This attack is the nature of eavesdropping on, or monitoring of, transmissions.

 Cryptography is used to hide information. It is not only use by spies but for phone, fax and e-mail communication, bank transactions, bank account security, PINs, passwords and credit card transactions on the web. It is also used for a variety of other information security issues including electronic signatures, which are used to prove who sent a message. Cryptography is a key technology in electronic key systems. It is used to keep data secret, digitally sign documents, access control, and so forth. Users therefore should not only know how its techniques work, but they must also be able to estimate their efficiency and security

 

The Open Systems Interconnection (OSI) security architecture provides a systematic framework for defining security attacks, mechanisms, and services.

 Security attacks are classified as either passive attacks, which include unauthorized reading of a message of file and traffic analysis or active attacks, such as modification of messages or files, and denial of service.

A security mechanism is any process (or a device incorporating such a process) that is designed to detect, prevent, or recover from a security attack. Examples of mechanisms are encryption algorithms, digital signatures, and authentication protocols.

 Security services include authentication, access control, data confidentiality, data integrity, nonrepudiation, and availability.

The field of network and Internet security consists of measures to deter, prevent, detect, and correct security violations that involve the transmission of information.

1.3      Examples of security violation

 

1.                 User A transmits a file to user B. The file contains sensitive information (e.g., payroll records) that is to be protected from disclosure. User C, who is not authorized to read the file, is able to monitor the transmission and capture a copy of the file during its transmission.

2.                 A network manager, D, transmits a message to a computer, E, under its management. The message instructs computer E to update an authorization file to include the identities of a number of new users who are to be given access to that computer. User F intercepts the message, alters its contents to add or delete entries, and then forwards the message to computer E, which accepts the message as coming from manager D and updates its authorization file accordingly.

3.                 Rather than intercept a message, user F constructs its own message with the desired entries and transmits that message to computer E as if it had come from manager D. Computer E accepts the message as coming from manager D and updates its authorization file accordingly.

4.                 An employee is fired without warning. The personnel manager sends a message to a server system to invalidate the employee’s account. When the invalidation is accomplished, the server is to post a notice to the employee’s file as confirmation of the action. The employee is able to intercept the message and delay it long enough to make a final access to the server to retrieve sensitive information. The message is then forwarded, the action taken, and the confirmation posted. The employee’s action may go unnoticed for some considerable time.

A message is sent from a customer to a stockbroker with instructions for various transactions. Subsequently, the investments lose value and the customer denies sending the message.

 

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).

This definition introduces three key objectives that are at the heart of computer security:

• Confidentiality: This term covers two related concepts: Data confidentiality: Assures that private or confidential information is not made available or disclosed to unauthorized individuals. Privacy: Assures that individuals control or influence what information related to them may be collected and stored and by whom and to whom that information may be disclosed.

• Integrity: This term covers two related concepts: Data integrity: Assures that information and programs are changed only in a specified and authorized manner. System integrity: Assures that a system performs its intended function in an unimpaired manner, free from deliberate or inadvertent unauthorized manipulation of the system.

• Availability: Assures that systems work promptly and service is not denied to authorized users.

These three concepts form what is often referred to as the CIA triad. The three concepts embody the fundamental security objectives for both data and for information and computing services.

Requirements of Security

·                     Confidentiality: Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information. A loss of confidentiality is the unauthorized disclosure of information.

·                     Integrity: Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity. A loss of integrity is the unauthorized modification or destruction of information.

·                     Availability: Ensuring timely and reliable access to and use of information. A loss of availability is the disruption of access to or use of information or an information system.

 Impact on Breach of Security

Three levels of impact is identified on organizations or individuals should there be a breach of security :- Low, Moderate, High.

Examples  

·         Confidentiality: Student grade information(H), student enrollment info(M) , list of students(L).

What if the data is can be read by all and no confidentiality at all.

·         Integrity : Patient Medical Record(H) , Forum(M) , Anonymous online poll(L)

What if the data is changed ? How seriously it can affect the system ?

·         Availability: Information for  Critical tasks(H) , Public website(M), Telephone look up directory(L)

What if the data is not available at the proper time ?

THE OSI SECURITY ARCHITECTURE

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.

Threat

A potential for violation of security, which exists when there is a circumstance, capability, action, or event that could breach security and cause harm. That is, a threat is a possible danger that might exploit a vulnerability.

Attack

An assault on system security that derives from an intelligent threat; that is, an intelligent act that is a deliberate attempt (especially in the sense of a method or technique) to evade security services and violate the security policy of a system.

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

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

•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.

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

A useful means of classifying security attacks, used both in X.800 and RFC 2828, is in terms of passive attacks and active attacks. A passive attack attempts to learn or make use of information from the system but does not affect system resources. An active attack attempts to alter system resources or affect their operation.

Passive Attacks

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 the release of message contents and traffic analysis.

A telephone conversation, an electronic mail message, and a transferred file may contain sensitive or confidential information. We would like to prevent an opponent from

learning the contents of these transmissions.

Suppose that we had a way of masking the contents of messages or other information traffic so that opponents, even if they captured the message, could not extract the

information from the message. The common technique for masking contents is encryption. If we had encryption protection in place, an opponent might still be able to observe the pattern of these messages. The opponent could determine the location and identity of communicating hosts and could observe the frequency and length of messages being exchanged. This information might be useful in guessing the nature of the communication that was taking place.

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 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.

A masquerade takes place when one entity  pretends to be a different entity

A masquerade attack usually includes one of the other forms of active attack. For example, authentication sequences can be captured and replayed after a valid authentication sequence has taken place, thus enabling an authorized entity with few privileges to obtain extra privileges by impersonating an entity that has those privileges. Replay involves the passive capture of a data unit and its subsequent retransmission to produce an unauthorized effect

Modification of messages simply means that some portion of a legitimate message is altered, or that messages are delayed or reordered, to produce an unauthorized effect .

For eg, a message meaning “Allow John Smith to read confidential file accounts” is modified to mean “Allow Fred Brown to read confidential file accounts.”

The denial of service prevents or inhibits the normal use or management of communications facilities. This attack may have a specific target; for example, an entity may suppress all messages directed to a particular destination (e.g., the security audit service).Another form of service denial is the disruption of an entire network, either by disabling the network or by overloading it with messages so as to degrade performance.

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. If the detection has a deterrent effect, it may also contribute to prevention.

 Security  services are the services within a computer system that protect its resources.

Identifiation & Authentication

 Identifiation is being able to identify uniquely a user of a system or an application that is running in the system.  Authentication is being able to prove that a user or application is genuinely who that aperson or what that application claims to be.

Eg: A user logs onto a system using a user id and password. The sytem uses userid  to identify and authenticates the user by checking that the supplied password is correct.

The access control service protects critical resources in a system by limiting access only to authorized users and their applications. It prevents the unauthorized use of a resource or the use of a resource in an unauthorized manner.

Eg: Only authorised admin can issue command  to manage a system.
     Only  some authorised users are permitted to get internet services

The confidentiality service protects sensitive information from unauthorized disclosure.

Sensitive data should be encrypted when it is transmitted over a communications network, especially over an insecure network such as the Internet. In a networking environment, access control mechanisms are not effective against attempts to intercept the data, such as wiretapping.

The data integrity service detects whether there has been unauthorized modification of data. There are two ways in which data might be altered: accidentally, through hardware and transmission errors, or because of a deliberate attack. Many hardware products and transmission protocols now have mechanisms to detect and correct hardware and transmission errors. The purpose of the data integrity service is to detect a deliberate attack.

The data integrity service aims only to detect whether data has been modified. It does not aim to restore data to its original state if it has been modified.

Non Repudiation

The non-repudiation service can be viewed as an extension to the identification and authentication service. In general, non-repudiation applies when data is transmitted electronically; for example, an order to a stock broker to buy or sell stock, or an order to a bank to transfer funds from one account to another. The overall goal is to be able to prove that a particular message is associated with a particular individual.

The non-repudiation service can contain more than one component, where each component provides a different function. If the sender of a message ever denies sending it, the non-repudiation service with proof of origin can provide the receiver with undeniable evidence that the message was sent by that particular individual. If the receiver of a message ever denies receiving it, the non-repudiation service with proof of delivery can provide the sender with undeniable evidence that the message was received by that particular individual.

Security mechanisms are technical tools and techniques that are used to implement security services. A mechanism can operate by itself of with other mechanism to provide a service.

An access control list (ACL), with respect to a computer file system, is a list of permissions attached to an object. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject and an operation. For instance, if a file has an ACL that contains (Alice, delete), this would give Alice permission to delete the file.

Cryptography is the process of converting between readable text, called plaintext, and an unreadable form, called ciphertext:

1. The sender converts the plaintext message to ciphertext. This part of the process is called encryption (sometimes encipherment).
2. The ciphertext is transmitted to the receiver.
3. The receiver converts the ciphertext message back to its plaintext form. This part of the process is called decryption (sometimes decipherment).

The conversion involves a sequence of mathematical operations that change the appearance of the message during transmission but do not affect the content. Cryptographic techniques can ensure confidentiality and protect messages against unauthorized viewing (eavesdropping), because an encrypted message is not understandable.

Digital Signatures

A digital signature or digital signature scheme is a mathematical scheme for demonstrating the authenticity of a digital message or document. A valid digital signature gives a recipient reason to believe that the message was created by a known sender, and that it was not altered in transit. Digital signatures are commonly used for software distribution, financial transactions, and in other cases where it is important to detect forgery or tampering.

What is an eavesdropping attack?

Is eavesdropping a passive attack?

What type of attack allows attackers to eavesdrop on the communication between two targets?

What is the attack and passive attack?