A Computer is a machine used to perform data process function. The information is fed into the computer through the input devices attached to the system. The raw information is then processed in the Central Processing Unit (CPU) to give out the output, which will be displayed in the Visual Display Unit (VDU) or printed out to get the computer hard copy.
During the earlier days of computer development, emphasis was focused principally on mechanical and electronic considerations on the automating of calculations. The idea was to do everything possible to build bigger, faster computing equipment and deliver computing machinery. Convenience in using machine wasn't important. It was in this light that the first large scale digital computer- the ENIAC (Electronic Numerical Integrator Calculator) was built in 1946.
This device which contained more than 18,000 vacuum tubes and 6,000 electric switches weighed 2 tonnes and occupied more than 1,500 square feet of floor space. By today's standard, ENIAC was a massive, plodding dinosaur. In 1964, it was a wonder-capable of performing calculations 1000 times faster than existing electromechanical devices.
In addition, the ENIAC was controlled through external switches that set the various circuits in the desired computational patterns. Once "instructed" by this combination of switches, the computer could carryout the calculation without human intervention. However to change a "program" the operator had to disconnect wires and reset switches by hand, a task that required several hours. While this work was going on, the computer was unproductive. This cumbersome "programming" effort offset many of the advantages of the automatic computing. It became evident that a capability was needed for computers to store instructions electronically- in the same way data were stored.
2.2 MAIN BODY
GENERAL VIEW OF COMPUTER VIRUS
This section will be looking at contributions from famous writers and professional opinions as regards relevant literature in the light of computer viruses.
Azuka (1996) stated that "computer viruses are programs designed to replicate and spread sometimes without indicating that they exist".
The ITrain Collective Computer Handbook (1998), states "Viruses are realâ€¦.but please don't panicâ€¦. Computers get infected and most survive".
In view of Prenum (1992), "a computer virus is a piece of software which attaches itself to another program on a system in other to spread itself to other programs and to have some undesirable effects on the programs it becomes attached to.
Nance (1989) defined a computer virus as actually a small undetected program that overtime infects other program and eventually disables the entire system.
He clearly put it that a typical virus might contain the following instructions:
Temporarily suspend the execution of main program
Search the computer memory for other likely uninfected hosts
If found, inserts a copy of these instruction
Return control of computer back to host program.
Computer viruses may be grouped into two major categories namely Destructive Viruses and Non- Destructive Viruses.
In this view Akinyokun (1994) explains that the Destructive type can either be massive, partial, selective, random haux and network saturation.
Massive Destructive viruses attack the format of the hard disk or floppy disk whereby any program or data damaged will not be recoverable. The Partial type causes the erasure or modification of specific files like the executable and command files. The random haux virus randomly changes data on disk or main memory (RAM or ROM) during normal program execution or file processing, while the network saturation virus systematically uses up the computer memory or space to impede performance or cause the system to crash. While the Non- Destructive viruses usually cause annoyance. They may display messages, change display colour, change the effect of some controlled keys of the keyboard, delete characters displayed on monitor or play some music at regular interval for a short period of time. Various types of these will be explained in the next chapter.
In general, a computer virus may slow down the speed of computer, cause irregular screen activity and corrupt storage media, application and system software.
2.2.1 REASONS FOR VIRUS
Computer Viruses didn't just emanated from space, people write them. They design the attack phase by writing the code, test it to make sure it spreads properly and then release it. And such release which can appear as a silly message on your screen can cause the destruction of a hard disk. But why should anyone conceive such evil? This work has been able to identify at least four reasons for such.
The first is the same psychology that drives people that vandalize properties.
Why would someone want to break a window or someone's car, paint signs on buildings or burn down a beautiful forest? For some people, that seems to be fun. If that sort of person knows computer programming, then he or she may have more than enough energy into the creation of destructive viruses.
The second reason has to do with the excitement of watching things blow up.
Some people have a fascination with things like explosions and car wrecks. When you were growing up, there might have been a kid in your neighborhood who learned how to make gunpowder. And that kid probably built bigger and bigger bombs until he either got bored or did some serious damage to himself. Creating a virus is a little like that -- it creates a bomb inside a computer, and the more computers that get infected the more "fun" the explosion.
The third reason has to do with ego.
If you are a certain type of programmer who sees a security hole that could be exploited, you might simply be compelled to exploit the hole yourself before someone else takes the glory.
The fourth reason is software protection.
Software piracy has been in vogue in recent years. According to Longman dictionary (1995), piracy means an illegal copying and sale of books, tapes video. e.tc.
Organization like Microsoft Corporation is leading in the production of marketable software packages. Piracy has posed a threat to the successful sales of this software. Attempts have been made to reduce this enigma. That is why over the decades, copyright law has been the major way of software protection.
But irrespective of this laws computer users have still be pirating into such software. That is why some of this organization has written viruses into the internet as a means of checkmating such unlicensed users that go into their privacy, without permission.
No wonder the Pentagon- a most military top-secret computer in the US is kept in electronically shielded rooms and when necessary, connected with wire that runs through pipes filled with gas under pressure. The gas pressure will drop if someone attempts to penetrate the pipes to trap the viruses.
But be that as it may, most virus creators seem to miss the point that they cause real damage to real people with their creations. Destroying everything on a person's hard disk is real damage. Forcing a large company to waste thousands of hours cleaning up after a virus is real damage. Even a silly message is real damage because someone has to waste time getting rid of it. For this reason, the legal system is getting much harsher in punishing the people who create viruses.
2.2.2 TYPES OF COMPUTER
Computers types in this work will be classified taking into consideration certain features like size, portability, speed of processing and storage capacity.
A relatively light, portable, compact type of computer is the most common of all. They are light systems used by individuals to process small amount of data. They can be used in schools, business places and homes.
Examples are Desktop computers (monitor is placed on top the system unit), Tower Systems (monitor is placed by the side of system units), Laptop Computer, Notebook computer and Palmtop computers.
Developed in the 1970s for specialized task i.e they are special purpose computers. They are bigger compared to the microcomputers but smaller and less powerful and even less expensive than mainframes. Examples are HEWLETT PACKARD 3000, IBM system 38, MV 400
MIDRANGE COMPUTERS AND MAINFRAMES
Large systems installed in most organizations to carry out data processing function. They are used to interconnect people to work from other terminals without being aware of the presence of the others. They are more powerful than the micro and mini computers. Examples are IBM 360/370 systems, NCR V-8800 system.
The most powerful of all computers, they are designed to solve problems consisting of long and difficult calculations. Examples are A Cray x-mp super computer
Because software is often designed with security features to prevent unauthorized use of system resources, many viruses must exploit software in a system or application to spread.
Software is the general term for the set of programs and data which direct the hardware on what to do. Without software computers cannot carry out specific tasks that it is expected to perform. They are subdivided into two types namely System Software (designed to handle technical details) and Application software (focuses on completing specific tasks or application). Examples of software are Windows XP, UNIX, LINUS, Microsoft Excel e.t.c
2.2.4 STORAGE DEVICES SUSCEPTIBLE TO VIRUS ATTACK
Storage in computer is the process of retaining information for future use.
A computer cannot function with only processing, input and output devices. To be really useful however it needs a place to keep program files and related data when they are not in use. Such storage device can either be magnetic, optical, flexible, disk controller interfaces and Hard disk. Examples of these devices are the cassette magnetic tapes, WORM disc, CD ROMs, DVD, floppy discs, IDE, SCSI, USB flash disc, fire wire, disk cache and Seagate hard disc e.t.c.
But be that as it may the devices were these data are kept can be attacked by virus. Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks.
In the early days of the personal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. Personal computers at that time would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the world for many years.
2.3 SUMMARY OF LITERATURE REVIEW
The destructive capabilities of computer virus to computer business in systems and industries have so created a lot of wave in the society that there is call for more concern amongst computer users. Cohen insist that "it's better to have somebody friendly to the experiment, tell you how bad it is, show you how it works and help you counteract it than to have somebody vicious come along and do it. " if you wait it might be too late"