2Chapter 1 – Introduction The art of war teaches us to rely not on the likelihood of the enemy's not coming, but on our own readiness to receive him; not on the chance of his not attacking, but rather on the fact that we have made our position unassailable.—The Art of War, Sun Tzu
3BackgroundInformation Security requirements have changed in recent timestraditionally provided by physical and administrative mechanismscomputer use requires automated tools to protect files and other stored informationuse of networks and communications links requires measures to protect data during transmissionTraditionally information security provided by physical (eg. rugged filing cabinets with locks) and administrative mechanisms (eg. Personnel screening procedures during hiring process).Growing computer use implies a need for automated tools for protecting files and other information stored on it.This is especially the case for a shared system, such as a time-sharing system, and even more so for systems that can beaccessed over a public telephone network, data network, or the Internet.
4IntroductionTraditionally information security provided by physical (eg. rugged filing cabinets with locks) and administrative mechanisms (eg. Personnel screening procedures during hiring process).Growing computer use implies a need for automated tools for protecting files and other information stored on it.This is especially the case for a shared system, such as a time-sharing system, and even more so for systems that can beaccessed over a public telephone network, data network, or the Internet.
5DefinitionsComputer Security - generic name for the collection of tools designed to protect data and to thwart hackersNetwork Security - measures to protect data during their transmissionInternet Security - measures to protect data during their transmission over a collection of interconnected networks
6Aim of Course our focus is on Network and Internet Security consists of measures to determine, prevent, detect, and correct security violations that involve the transmission of information
7Threat and Attack : DefThreat: A potential for violation of security, which exists when there is a circumstance. Capability, action, or event that could breach security and cause harm.Attack : An assault on system that derives from an intelligent threat I.e an Intelligent act to evade security services.
8Attack, Mechanism and Service Let us consider three aspects of information security:security attacksecurity mechanismsecurity servicePlease consider in reverse order so that easy to understand
9Security ServiceSecurity Service is something that enhances the security of the data processing systems and the information transfers of an organizationintended to counter security attacksmake use of one or more security mechanisms to provide the servicereplicate functions normally associated with physical documentseg have signatures, dates; need protection from disclosure, tampering, or destruction; be notarized or witnessed; be recorded or licensed
10Security Service cont.. Authentication: This is a service that is concerned with assuring that a communication is authentic.This will ensure the recipient that the message is from the source that it claims to be from.2 aspects such as, time of connection initiation and assurance of connection is not interfered
11Security Service Peer entity authentication: This provides the identity of a peer entity in an association. It also establishes of data transfer during the run time. It attempts to provide confidence that any entity is not performing either a masquerade or an unauthorized replay of previous connection.Data Origin authentication:This provides the source of data unit and does not provide the duplication of data. This supports application like where there are no prior interactions between the communicating entities.
12Security Service cont Data Confidentiality: Confidentiality is the protection of transmitted data from passive attackswith respect to data transmission several level of protection can be identified.The broad cast service protects all user data transmitted between two systems.Data Integrity:A connection oriented integrity that deals with a stream ofmessages with assurance that messages are sent, without anyduplication, insertion and modification.
13Security Mechanisma mechanism that is designed to detect, prevent, or recover from a security attackno single mechanism that will support all functions requiredhowever one particular element underlies many of the security mechanisms in use: cryptographic techniques
14Security Attackany action that compromises the security of information owned by an organizationinformation security is about how to prevent attacks, or failing that, to detect attacks on information-based systemshave a wide range of attackscan focus of generic types of attacksnote: often threat & attack mean samecf. Table 1.2 for examples of security attacks, and Table 1.3 for definitions of threat and attack
15Security Attack cont..Passive AttackPassive attach are in the way of monitoring of transmission.The goal is to obtain information that is being transmittedRefer figure 1.3 in page 8 of you bookpassive attacks - eavesdropping on, or monitoring of, transmissions to:obtain message contents, ormonitor traffic flows
17Classify Security Attacks as active attacks – modification of data stream to:masquerade of one entity as some otherreplay previous messagesmodify messages in transitdenial of serviceRefer figure 1.4 in page 9 of your book
18OSI Security Architecture ITU-T X.800 Security Architecture for OSIdefines a systematic way of defining and providing security requirementsfor us it provides a useful, if abstract, overview of concepts we will study
19Security ServicesX.800 defines it as: a service provided by a protocol layer of communicating open systems, which ensures adequate security of the systems or of data transfersRFC 2828 defines it as: a processing or communication service provided by a system to give a specific kind of protection to system resourcesX.800 defines it in 5 major categories
20Security Services (X.800)Authentication - assurance that the communicating entity is the one claimedAccess Control - prevention of the unauthorized use of a resourceData Confidentiality –protection of data from unauthorized disclosureData Integrity - assurance that data received is as sent by an authorized entityNon-Repudiation - protection against denial by one of the parties in a communicationSee Table 1.4 for details of the 5 Security Service categories and the 14 specific services.
22Security Mechanisms (X.800) specific security mechanisms:encipherment, digital signatures, access controls, data integrity, authentication exchange, traffic padding, routing control, notarizationpervasive security mechanisms:trusted functionality, security labels, event detection, security audit trails, security recoverysee Table 1.3 for details of these mechanisms, and Table 1.4 for the relationship between services and mechanisms.see Table 1.5 for details of these mechanisms, and Table 1.6 for the relationship between services and mechanisms.The “specific security mechanisms” are protocol layer specific, whilst the “pervasive security mechanisms” are not.Will meet some of these mechanisms in much greater detail later.
24In considering the place of encryption, its useful to use the following two models. The first models information flowing over an insecure communications channel, in the presence of possible opponents. Hence an appropriate security transform (encryption algorithm) can be used, with suitable keys, possibly negotiated using the presence of a trusted third party.
25Model for Network Security using this model requires us to:design a suitable algorithm for the security transformationgenerate the secret information (keys) used by the algorithmdevelop methods to distribute and share the secret informationspecify a protocol enabling the principals to use the transformation and secret information for a security service
26Model for Network Access Security Stallings Fig 1-4.The second model is concerned with controlled access to information or resources on a computer system, in the presence of possible opponents. Here appropriate controls are needed on the access and within the system, to provide suitable security. Some cryptographic techniques are useful here also.
27Model for Network Access Security using this model requires us to:select appropriate gatekeeper functions to identify usersimplement security controls to ensure only authorised users access designated information or resourcestrusted computer systems can be used to implement this model
28Summary We have considered: computer, network, internet security def’s security services, mechanisms, attacksX.800 standardmodels for network (access) security