CHAPTER TWO
2.0 LITERATURE REVIEW
2.2 NETWORK SECURITY
As we have already discussed that the fast development of the modern Internet technology and information technology cause the individual, enterprise, school and government department joining the Internet, Which cause more illegal users to attack and destroy the network by using the fake websites, fake mail, Trojan horse and backdoor virus at the same time. So we need some type of security to protect our networks from such malicious users. Network security mainly consists of the technologies and the processes that are deployed to protect internal networks from external threats. The primary goal of network security is to provide controls along the network perimeter which allow access to the internal network and only let traffic pass if that traffic is authorized, valid, and of acceptable risk. One thing should always be kept in mind that network security controls cannot completely eliminate the risk. The goal is to minimize risk as much as possible and to avoid unnecessary or excessive risk.
2.2 CHARACTERISTICS OF NETWORK SECURITY
Network security has the following four basic characteristics:
1. Data Integrity: it means the data cannot be changed without the authorization that is, only people who can be allowed can modify data, and can determine whether data has been modified.
2. The confidentiality of the data: this states that data cannot be leaked to unauthorized users for their use. Data encryption is used to achieve this goal. By encrypting the data in transmission and use it can be protected from illegal access by third parties.
3. Data availability: it states that data is not available to all the users at all the time. It means that only authorized users can access and use the data and data is made available only on demand.
4. Data controllable: that can control the flow of information and the behavior patterns within the mandate, such as access to data, communication and content with the control. System must be able to control who can access the system or network data, and how to access at the same time, be able to authenticate users on the network, and record the network activity of all users.
2.4 MAIN THREATS TO NETWORK SECURITY
From a technical point of view, the network insecurity, on the one hand because of all the resources through a network share, on the other hand its technology is open. In general, network security threats are the following:
1. Inadvertent human error: improper use of operators, security configuration vulnerabilities, user with poor security awareness, choosing inadvertently a password will pose a threat to network security.
2. Man-made malicious attacks: such attacks are divided into two kinds: one is the active attacks, its purpose is to tamper with the information contained in the system, or to change the system's state and operation in variety of ways and to destroy it validity, integrity and authenticity; the other is a passive attack, it does not affect the normal work of the network, intercept and theft information, strong threat confidentiality of the system.
3. "Back door" of networking software and loopholes: all network software cannot be 100% free from vulnerabilities which are a prime target for hacker attacks. Thus due to their own vulnerability the corresponding system and application software are targeted by the hackers.
4. Non-authorized access: the use of network or computer resources without their consent is seen as a non-authorized access. Mainly in the following forms: the illegal users by impersonating the identity access the network for illegal operation; authorized users in lawful manner operate and so on.
2.4 SOLUTION OF NETWORK SECURITY PROBLEM
A. Firewalls
Firewalls may be defined as the network devices used to restrict traffic passing between networks. A fire wall can consist of hardware and software, or even several components working together. Firewalls are mainly used to implement security policies which govern the flow of traffic between two or more networks.
As a traditional security technology, the main function of firewall is to strengthen the visit restrictions between the networks and prevent the exterior network user from entering into the internal network by illegal method. If an intruder want access to the target computer; first of all, it must pass through firewall. By setting the visit rules to filtrate the visits which are not safely, it may enhance the network security enormously and reduce the risk of host.
Limitations of Firewalls are:
1. Firewall cannot prevent attacks coming from Intranet.
2. The access control policy of firewall is static, and cannot adapt itself to the change of the attack from outside.
3. Filtering rules of firewall are usually very simple, so firewall cannot prevent attacks coming from application layer, and cannot prevent viruses also.
B. Types of firewalls
There are mainly five types of firewalls and are given below:
1. Simple packet filter
2. State full inspection filter
3. Application proxy
4. Hybrid firewalls
5. Personal firewalls
Now we will explain all these type of firewalls one by one.
i. Simple packet filter):
