Types Of Computer Virus Sources Of Virus Virus Warning Signs Virus Detection(Anti-Virus) Virus Prevention and Removal

Transcription

1 DATA PROCESSING NOTES FOR SS THREE FIRST TERM 2016/2017 SESSION SCHEME OF WORK Week 3 Week 4 Continuation of Spreadsheet(Practical) Computer Virus Types Of Computer Virus Sources Of Virus Virus Warning Signs Virus Detection(Anti-Virus) Virus Prevention and Removal Week 5 Computer Networking Meaning of Network and Networking Network Topologies Types Of Computer Networks Intranet, Extranet And Internet Network Devices Benefits Of Computer Networks Week 6 Week 7-8 Database Security Parallel and Distributed Databases Architectures For Parallel Databases Parallel Query Evaluation Advantages Of Parallel Databases Disadvantages Of Parallel Databases Distributed Databases Types Distributed Databases Week 9 Crash recovery and Database Indexes Computer Ethics and Safety Measures (SS 1 data processing) Maintenance of computer I and II (SS2 and SS3 data processing) Career opportunities in data processing (SS3 data processing) 1

2 COMPUTER VIRUS Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. It is a program written by people called virus perpetrators or data invaders which often cause damage by attaching itself to another program and files on the computer system. A virus might corrupt or delete data on your computer, use your program to spread itself to other computers, or even erase everything on your hard disk. Computer viruses are often spread by attachments in messages or instant messages. That is why it is essential that you never open attachments unless you know who it's from and you are expecting it. DEFINITION A computer virus is a piece of software that attaches itself to another program to corrupt the program and files on the computer system. Types of Computer Virus Computer Viruses are classified according to their nature of infection and behavior. Different types of computer virus classification are given below. 1. Resident virus: They usually fix themselves inside the computer memory. They get activated every time the OS runs and end up infecting other opened files.they hide in RAM.Examples CMJ,Randex,Mrklunky etc. 2. Overwrite Virus: These types of viruses delete any information in a file they infect, leaving them partially or completely useless once they are infected. Once in the computer, they replace all the file content but the file size doesn t change.examples trivial.88.d,trj.reboot etc 3. Boot sector: A Boot Sector Virus infects the first sector of the hard drive, where the Master Boot Record (MBR) is stored.. If a computer is infected with Boot Sector Virus, when the computer is turned on, the virus launches immediately and is loaded into memory, enabling it to control the computer. examples poly boot,antiexe,stone virus,disk killer,form etc 4. Macro virus: Macro viruses infect files that are created using certaing applications e.g ms office suite, these macros are usually stored as part of the document or spreadsheet and can travel to other systems when these files are transferred to another computer.examples Relax,Bablas etc 5. Directory Virus: Also known as cluster virus or file system virus. They infect the computer s directory by changing the path indicating file location. They are usually located in the disk but affect the entire directory. Example is any file with the extension.exe or.com 2

3 6. Polymorphic virus: Polymorphic Viruses have the capability to change their appearance and change their code every time they infect a different system.this helps the Polymorphic Viruses to hide from anti-virus software.examples are Elkern,Marburg,etc. Effects of virus It causes computer to crash (i.e. to stop functioning normally or to stop responding to other software) Loss of files and corruption of data stored in file. Virus warning signs When a computer is infected with virus, the following symptoms may occur Slow system performance Presence of tiny dots Incomplete saving of files Appearance of strange characters Corruption of the system set up instructions Wandering across the screen New windows keep opening up at an alarming rate when files and folders getting deleted when disks and drives are not working properly Sources of Virus Infected storage devices such as flash drive,cd-rom etc By downloading or opening attachments in from unknown source Through internet download Installation of infected programs opening an infected document by downloading cracked and illegal versions of software MALWARE PROGRAMS Malware is an abbreviated term meaning malicious software.it is a program that is specifically designed to gain access to or damage the computer files without the knowledge of the owner. It is developed for the purpose of doing harm to files, software and hardware.computer Virus is one of the examples of malware. Other malware programs include; Computer Worm: This is a program that uses computer network to spread itself. 3

4 Trojan Horses: This is illegal instructions placed in the middle of a legitimate program.it is hidden program that runs on your computer without your knowledge. Logic Bombs: This type of malware do not replicate, they are designed to destroy data on the computer system once certain conditions have been met. Spyware: It is written to spy through a legal software.it changes computer s configuration and personal information. VIRUS DETECTION SOFTWARE (ANTI-VIRUS) This is a program written by the programmer to get rid of computer viruses. Some anti-virus are programmed to kill the virus and the effect done to the computer while others prevent the virus from entering the computer system. Anti-virus software is computer software used to prevent, detect and remove malicious software. Examples are; karpersky,e-scan,avast,mcafee, etc Assignment one 1. List six examples of Anti-virus 2. What are the methods through which you can prevent your computer from virus infection.(list atleast 7) 3. What are the corrective measures to be taken in order to remove a virus from an infected computer. NETWORKING INTRODUCTION A network is nothing more than a group of computers and other communicating devices connected together so that they can exchange information and share resources. Computer networks can be found in large Businesses, Government offices, Institutions, Hospitals and so on. All over the world, millions of computers are being linked together in network, from local area networks to wide area networks to form internet. Networks are built with a mixture of computer hardware and software. 4

5 DEFINITION A computer network often referred to as a network is a collection of computers and other communicating devices connected together to enable them share resources and information. NETWORKING: This is the process or practice of linking two or more computing devices for the purpose of sharing resources and information. Network Elements Servers Clients/workstations Shared data Resources like printer, files, and other hardware and software resources Protocols Network Cables e.g UTP, STP, Coaxial, Fibre Optics. User INTRANET, EXTRANET AND INTERNET INTRANET An intranet is a private network belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. It may consist of many interlinked local area networks. Intranet is also referred to as a website within your company's network that (mostly) only employees can access. EXTRANET An extranet is an intranet that is accessible to some people from outside the company, or possibly shared by more than one organization.it is A network based on Web technologies that links selected resources of the intranet of a company with its customers, suppliers, or other business partners The difference between internet and intranet is that Intranet uses the internet protocols such as TCP/IP and FTP. Intranet sites are accessible via web browser in similar way as websites in internet. But only members of Intranet network can access intranet hosted sites. TYPES OF NETWORK Personal Area Network (PAN): This is a computer network used for data transmission among devices such mobile computers, cell phone within the range of an individual person. 5

6 1. Local Area Network (LAN): This is a number of computers and other devices connected together by cable or wireless media that communicate with one another within a small geographical area e.g. a building. 2. Metropolitan Area Network (MAN): This is a network that interconnects users with computer resources in a geographic area or region larger than that covered by a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). MANs are formed by connecting multiple LANs. Thus, MANs are extremely efficient and provide fast communication via high-speed carriers, such as fiber optic cables. Eg state government connect to staff communicate with each other anywhere within Lagos 3. Wide Area Network (WAN): A wide area network (WAN) is a network that exists over a large-scale geographical area. A WAN connects different smaller networks, including local area networks (LAN) and metro area networks (MAN). This ensures that computers and users in one location can communicate with computers and users in other locations. WAN implementation can be done either with the help of the public transmission system or a private network. NETWORK DEVICES Network devices are components used to connect computers or other electronic devices together so that they can share files or resources like printers. They include; Hub, Switch, Router, Brouter, Modem, Network Interface Card NETWORK TOPOLOGY This is referred to as the physical arrangement or layout of computer and other component on a network. TYPES OF NETWORK PROTOCOL Bus topology Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology Features of Bus Topology 1. It transmits data only in one direction. 2. Every device is connected to a single cable Advantages of Bus Topology 6

7 1. It is cost effective. 2. Cable required is least compared to other network topology. 3. Used in small networks. 4. It is easy to understand. 5. Easy to expand joining two cables together. Disadvantages of Bus Topology 1. Cables fails then whole network fails. 2. If network traffic is heavy or nodes are more the performance of the network decreases. 3. Cable has a limited length. 4. It is slower than the ring topology. Star topology In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node. Advantages of Star Topology 1. Fast performance with few nodes and low network traffic. 2. Hub can be upgraded easily. 3. Easy to troubleshoot. 4. Easy to setup and modify. 5. Only that node is affected which has failed, rest of the nodes can work smoothly. Disadvantages of Star Topology 1. Cost of installation is high. 2. Expensive to use. 3. If the hub fails then the whole network is stopped because all the nodes depend on the hub. Ring topology It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device. Advantages of Ring Topology 1. Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data. 2. Cheap to install and expand 7

8 Disadvantages of Ring Topology 1. Troubleshooting is difficult in ring topology. 2. Adding or deleting the computers disturbs the network activity. 3. Failure of one computer disturbs the whole network. Tree Topology It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy. It is extension of bus and star topologies. CATEGORIES OF COMPUTER NETWORK There are two categories of networks 1. Peer-to-peer networks 2. Server-based networks(client-server network) 1. Peer-to-peer network: This is a network of computers configured to allow certain files and folders to be shared with everyone or with selected users. Peer-to-peer networks are quite common in small offices that do not use a dedicated file server. 2. A client-server network is a central computer, also known as a server, which hosts data and other forms of resources. Clients such as laptops and desktop computers contact the server and request to use data or share its other resources with it. ASSIGNMENT TWO 1. Mention two advantages of peer-to-peer and server based network 2. Mention two disadvantages of peer-to-peer and server based network Benefits of computer networks File sharing Resource sharing 8

9 Speed Security Internet access sharing ASSIGNMENT THREE 1. What is computer ethics 2. What are the responsible ways of using computer and the Internet 3. List four ways of misusing computer and the internet 4. State safety measures that need to be taken when using computer ASSIGNMENT FOUR 1. State four qualities of good computer professionals 2. List four computer professional bodies in Nigeria 3. State two primary functions of the following computer professionals Web Developer DATABASE SECURITY Database Administrator Network Engineer Hardware Engineer Network Administrator Database security refers to the collective measures used to protect and secure a database or database management software from illegitimate use and malicious threats and attacks. It is a broad term that includes a multitude of processes, tools and methodologies that ensure security within a database environment. Database security covers and enforces security on all aspects and components of databases. This includes: Data stored in database Database server Database management system (DBMS) Other database workflow applications Database security is generally planned, implemented and maintained by a database administrator and other information security professional. The three main objectives to consider when designing a secure database are; SECRECY, INTERGRITY AND AVAILABILITY. 9

10 The primary method used to protect data is limiting access to the data. This can be done through authentication, authorization, and access control. TYPES OF DATABASE SECURITY CONTROL The security requirement of a system are specified by means of a security policy which is then enforced by various security mechanisms. The different types of database security include; Access Control Access control in database security is the establishment of measures that minimize or totally avoid unauthorized access to database. The purpose of access control is to ensure that a user is only permitted to perform those operations on the database for which that user is authorized. Auditing Database auditing is used to track database access and user activity. Auditing can be used to identify who accessed database objects, what actions were performed, and what data was changed. Database auditing does not prevent security breaches, but it does provide a way to identify if breaches have occurred. Authentication Database authentication is the process or act of confirming that a user who is attempting to log in to a database is authorized to do so, and is only accorded the rights to perform activities that he or she has been authorized to do. DATABASE ADMINISTRATOR A Database Administrator is responsible for the performance, intergrity and security of a database. Also, a DBA is involved in the planning and development of database, as well as troubleshooting any issues on behalf of the user ROLE OF A DATABASE ADMINISTRATOR Installing and updating the database server and application tools Controlling and monitoring user access to the database Backing up and restoring databases Generating various reports by querying from database when needed Maintaining system security Monitoring and optimizing the performance of the database 10