SECURITY SERVICES
The classification of security services are as follows: Confidentiality: Ensures that the information in a computer system and transmitted information are accessible only for reading by authorized parties. E.g. Printing, displaying and other forms of disclosure. Authentication: Ensures that the origin of a message or electronic document is correctly identified, with an assurance that the identity is not false. Integrity: Ensures that only authorized parties are able to modify computer system assets and transmitted information. The modification includes writing, changing status, deleting, creating and delaying or replaying of transmitted messages. Nonrepudiation: Requires that neither the sender nor the receiver of a message is able to deny the transmission. Access control: Requires that access to information resources may be controlled by or the target system. Availability: Requires that computer system assets be available to authorized parties when needed.
SECURITY MECHANISMS
One of the most specific security mechanisms in use is cryptographic techniques. Encryption or encryption-like transformations of information are the most common means of providing security. Some of the mechanisms are
1 Encipherment
2 Digital Signature
3 Access Control
SECURITY ATTACKS
There are four general categories of attack which are listed below.
Interruption
An asset of the system is destroyed or becomes unavailable or unusable. This is an attack on availability e.g., destruction of the piece of hardware, cutting of a communication line or
Disabling of file management system.
Interception
An unauthorized party gains access to an asset. This is an attack on confidentiality. An unauthorized party could be a person, a program or a computer. e.g., wiretapping to capture data in the network, illicit copying of files
Modification
An unauthorized party not only gains access to but tampers with an asset. This is an attack on integrity. e.g., changing values in the data file, altering a program, modifying the contents of
messages being transmitted in a network.
Fabrication
An unauthorized party inserts counterfeit objects into the system. This is an attack on authenticity. e.g., insertion of the spurious message in a network or addition of records to a file.
A release of message contents: A telephone conversation, an e-mail message and a transferred file may contain sensitive or confidential information. We would like to prevent the opponent from learning the contents of these transmissions.
Traffic analysis: If we had encryption protection in place, an opponent might still be able to observe the pattern of the message. The opponent could determine the location and identity of communication hosts and could observe the frequency and length of messages being exchanged. This information might be useful in guessing the nature of communication that was taking place. Passive attacks are very difficult to detect because they do not involve any alteration of data. However, it is feasible to prevent the success of these attacks.
Masquerade – One entity pretends to be a different entity.
Replay – involves passive capture of a data unit and its subsequent transmission to produce an unauthorized effect.
Modification of messages –
Some portion of the message is altered or the messages are delayed or recorded, to produce an unauthorized effect.
Denial of service – Prevents or inhibits the normal use or management of communication facilities. Another form of service denial is the disruption of an entire network, either by disabling the network or overloading it with messages so as to degrade performance. It is quite difficult to prevent active attacks absolutely because to do so would require physical protection of all communication facilities and paths at all times. Instead, the goal is to detect them and to recover from any disruption or delays caused by them.
The classification of security services are as follows: Confidentiality: Ensures that the information in a computer system and transmitted information are accessible only for reading by authorized parties. E.g. Printing, displaying and other forms of disclosure. Authentication: Ensures that the origin of a message or electronic document is correctly identified, with an assurance that the identity is not false. Integrity: Ensures that only authorized parties are able to modify computer system assets and transmitted information. The modification includes writing, changing status, deleting, creating and delaying or replaying of transmitted messages. Nonrepudiation: Requires that neither the sender nor the receiver of a message is able to deny the transmission. Access control: Requires that access to information resources may be controlled by or the target system. Availability: Requires that computer system assets be available to authorized parties when needed.
SECURITY MECHANISMS
One of the most specific security mechanisms in use is cryptographic techniques. Encryption or encryption-like transformations of information are the most common means of providing security. Some of the mechanisms are
1 Encipherment
2 Digital Signature
3 Access Control
SECURITY ATTACKS
There are four general categories of attack which are listed below.
Interruption
An asset of the system is destroyed or becomes unavailable or unusable. This is an attack on availability e.g., destruction of the piece of hardware, cutting of a communication line or
Disabling of file management system.
Interception
An unauthorized party gains access to an asset. This is an attack on confidentiality. An unauthorized party could be a person, a program or a computer. e.g., wiretapping to capture data in the network, illicit copying of files
Modification
An unauthorized party not only gains access to but tampers with an asset. This is an attack on integrity. e.g., changing values in the data file, altering a program, modifying the contents of
messages being transmitted in a network.
Fabrication
An unauthorized party inserts counterfeit objects into the system. This is an attack on authenticity. e.g., insertion of the spurious message in a network or addition of records to a file.
Cryptographic Attacks
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. Passive attacks are of two types:A release of message contents: A telephone conversation, an e-mail message and a transferred file may contain sensitive or confidential information. We would like to prevent the opponent from learning the contents of these transmissions.
Traffic analysis: If we had encryption protection in place, an opponent might still be able to observe the pattern of the message. The opponent could determine the location and identity of communication hosts and could observe the frequency and length of messages being exchanged. This information might be useful in guessing the nature of communication that was taking place. Passive attacks are very difficult to detect because they do not involve any alteration of data. However, it is feasible to prevent the success of these attacks.
Active attacks
These attacks involve some modification of the data stream or the creation of a false stream. These attacks can be classified into four categories:Masquerade – One entity pretends to be a different entity.
Replay – involves passive capture of a data unit and its subsequent transmission to produce an unauthorized effect.
Modification of messages –
Some portion of the message is altered or the messages are delayed or recorded, to produce an unauthorized effect.
Denial of service – Prevents or inhibits the normal use or management of communication facilities. Another form of service denial is the disruption of an entire network, either by disabling the network or overloading it with messages so as to degrade performance. It is quite difficult to prevent active attacks absolutely because to do so would require physical protection of all communication facilities and paths at all times. Instead, the goal is to detect them and to recover from any disruption or delays caused by them.
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