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Note for Computer Security - CS By kishan chandra

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Cyber Security By Kumar Kishan Chandra

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1.Introduction about Network and Network Security Network :- A network is defined as a group of two or more computer systems linked together. Why Network ? Computer networks allow the user to access remote programs and remote databases either of the same organization or from other enterprises or public sources. Computer networks provide communication possibilities faster than other facilities. Because of these optimal information and communication possibilities, computer networks may increase the organizational learning rate, which many authors declare as the only fundamental advantage in competition. Types Of Network local-area networks (LANs): The computers are geographically close together (that is, in the same building). wide-area networks (WANs): The computers are farther apart and are connected by telephone lines or radio waves. campus-area networks (CANs): The computers are within a limited geographic area, such as a campus or military base. metropolitan-area networks MANs): A data network designed for a town or city. home-area networks (HANs): A network contained within a user's home that connects a person's digital devices. Computer Security The meaning of the term computer security has evolved in recent years. Before the problem of data security became widely publicized in the media, most people’s idea of computer security focused on the physical machine. Traditionally, computer facilities have been physically protected for three reasons: To prevent theft of or damage to the hardware To prevent theft of or damage to the information To prevent disruption of service Strict procedures for access to the machine room are used by most organizations, and these procedures are often an organization’s only obvious computer security measures. Today, however, with pervasive remote terminal access, communications, and networking, physical measures rarely provide meaningful protection for either the information or the service; only the hardware is secure. Nonetheless, most computer facilities continue to protect their physical machine far better than they do their data, even when the value of the data is several times greater than the value of the hardware. Why Do We Need Security? In the ever changing world of global data communications, inexpensive Internet connections, and fast-paced software development, security is becoming more and more of an issue. Security is now a basic requirement because global computing is inherently insecure. As your data goes from point A to point B on the Internet, for example, it may pass through several other points

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along the way, giving other users the opportunity to intercept, and even alter it. It does nothing to protect your data center, other servers in your network, or a malicious user with physical access to your EnGarde system. Security Models No Security In this simplest case, the approach could be a decision to implement no security at all. Security through Obscurity In this model, a system is secure simply because nobody knows about its existence and contents. This approach cannot work for too long, as there are many ways an attacker can come to know about it. Host Security In this scheme, the security for each host is enforced individually. This is a very safe approach, but the trouble is that it cannot scale well. The complexity and diversity of modem sites/organizations makes the task even harder. Network Security Network security is the security provided to a network from unauthorized access and risks. It is the duty of network administrators to adopt preventive measures to protect their networks from potential security threats. Computer networks that are involved in regular transactions and communication within the government, individuals, or business require security. The most common and simple way of protecting a network resource is by assigning it a unique name and a corresponding password. In this modern era, organizations greatly rely on computer networks to share information throughout the organization in an efficient and productive manner. Organizational computer networks are now becoming large and ubiquitous. Assuming that each staff member has a dedicated workstation, a large scale company would have few thousands workstations and many server on the network. It is likely that these workstations may not be centrally managed, nor would they have perimeter protection. They may have a variety of operating systems, hardware, software, and protocols, with different level of cyber awareness among users. Now imagine, these thousands of workstations on company network are directly connected to the Internet. This sort of unsecured network becomes a target for an attack which holds valuable information and displays vulnerabilities. In this chapter, we describe the major vulnerabilities of the network and significance of network security. In subsequent chapters, we will discuss the methods to achieve the same. Access control is a way of limiting access to a system or to physical or virtual resources. In computing, access control is a process by which users are granted access and certain privileges to systems, resources or information .In access control systems, users must present credentials before they can be granted access. In physical systems, these credentials may come in many forms, but credentials that can't be transferred provide the most security.

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Network Boundary Protection controls logical connectivity into and out of networks. For example, multiple firewalls can be deployed to prevent unauthorized access to the network systems. Also intrusion detection and prevention technologies can be deployed to defend against attacks from the Internet. Various Types of Access Control Securing Access to Network Devices Restricting access to the devices on network is a very essential step for securing a network. Since network devices comprise of communication as well as computing equipment, compromising these can potentially bring down an entire network and its resources. Paradoxically, many organizations ensure excellent security for their servers and applications but leave communicating network devices with rudimentary security. An important aspect of network device security is access control and authorization. Many protocols have been developed to address these two requirements and enhance network security to higher levels. User Authentication and Authorization User authentication is necessary to control access to the network systems, in particular network infrastructure devices. Authentication has two aspects: general access authentication and functional authorization. General access authentication is the method to control whether a particular user has “any” type of access right to the system he is trying to connect to. Usually, this kind of access is associated with the user having an “account” with that system. Authorization deals with individual user “rights”. For example, it decides what can a user do once authenticated; the user may be authorized to configure the device or only view the data. User authentication depends up on factors that include something he knows (password), something he has (cryptographic token), or something he is (biometric). The use of more than one factor for identification and authentication provides the basis for Multifactor authentication. Password Based Authentication At a minimum level, all network devices should have username-password authentication. The password should be non-trivial (at least 10 character, mixed alphabets, numbers, and symbols). In case of remote access by the user, a method should be used to ensure usernames and passwords are not passed in the clear over the network. Also, passwords should also be changed with some reasonable frequency. Centralized Authentication Methods Individual device based authentication system provides a basic access control measure. However, a centralized authentication method is considered more effective and efficient when the network has large number of devices with large numbers of users accessing these devices. Traditionally, centralized authentication was used to solve problems faced in remote network access. In Remote Access Systems (RAS), the administration of users on the network devices is not practical. Placing all user information in all devices and then keeping that information upto-date is an administrative nightmare. Centralized authentication systems, such as RADIUS and Kerberos, solve this problem. These centralized methods allow user information to be stored and managed in one place. These systems can usually be seamlessly integrated with other user account management schemes such as Microsoft’s Active Directory or LDAP directories. Most RADIUS servers can

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