However, viruses often trick the computer's operating system or the computer user into running the viral program. Some viruses have the ability to attach themselves to otherwise legitimate programs. This attachment may occur when the legitimate program is created, opened, or modified. When that program is run, so is the virus. Viruses can also reside on portions of the hard disk or floppy disk that load and run the operating system when the computer is started, and such viruses thereby are run automatically.
A computer virus is a software program that affects the computer operation and it can potentially damage the computer. A computer virus is attached to a program or a file which allows it to spread from one computer to another when the program is running. Most of the viruses are attached to an executable file which allows the virus to stay on the computer but cannot do any damage until you open or run the infected program. Viruses are capable of corrupting or deleting data from the computer. They can also infect other computers.
Programs are infected only once by most viruses. There are many ways a virus can infect you system. One way is, if the virus is a file infecting virus, when you run a file infected with that virus. This particular kind of virus can only infect if YOU run the program! This virus targets COM and EXE files, but have also been found in other executable files.
They spread by attaching themselves to other programs (such as your word processing or spreadsheet programs). Then when a file with a virus attached to it is executed the virus will also be executed. Viruses can also attach themselves to system files the computer uses every time it is switched on, these are called boot sector viruses, and can cause persistent and widespread disruption to the computer. Viruses can also infest documents such as those created with a word processor. Infested documents are stored with a list of instructions called a macro, which is essentially a mini program.
Computer Viruses A computer virus is an illegal and potentially damaging computer program designed to infect other software by attaching itself to any software it contacts. In many cases, virus programs are designed to damage computer systems maliciously by destroying of corrupting data. If the infected software is transferred to or accessed by another computer system, the virus spreads to the other system. Viruses have become a serious problem in recent years, and currently, thousands of known virus programs exist (Reed 85-102)b. Three types of viruses are a boot sector virus, file virus, and Trojan horse virus.
Sometimes viruses might cause random damage to data files and over a long period of time they might destroy files and disk (Hanhisalo). Boot viruses are infected floppy disk that boot records or master boot records in hard disks. They replace copying it elsewhere on the disk overwriting it. Boost viruses load into memory if the computer tries to read it while it is booting. Examples of a boot virus are Form, Disk Killer, Michelangelo, and Stone virus.
(Yang, 1998) A computer virus can be as "evil as it sounds, snakingits way into personal computers, posing an occasional annoyance or a seriousthreat to all data." (Miastkowski, 1998) Symptoms can range from unpleasantto fatal. Computer viruses spread from program to program and computer tocomputer, "much as biological viruses spread within individual...members of asociety." (Chess, 1997) Diskettes were the "primary carriers of viruses inthe 1980s." ("Computer," 1997) Today, they are e-mail attachments, filetransfers and infected software downloads or uploads.
Computer Virus and Components A computer virus can be defined as a rogue computer program, usually short in nature, designed to spread copies of itself to other computers and disrupt the computers’ normal operation. These viruses usually attach or insert themselves in or to a program or boot sector of a disk. It is spread through floppy disk, network, or routine on-line services. There are some viruses that are harmless, but others can destroy or corrupt data and cause an operating system or application program to malfunction. The three most common types of destructive computer programs are the Trojan horse, logic bombs, and the worm.
When an infected file is activated, or when the computer is started from an infected disk, the virus itself is also activated. Many times a virus will lurk in a computers memory, waiting to infect the next program or disk that is activated. What makes viruses so dangerous is their ability to perform an event. While some events are harmless like displaying a message on a certain date, and others annoying, like slowing performance or altering the screen display, some viruses can be disastrous by damaging files, and destroying data. Most viruses are created out of curiosity.
The logic kill is a virus triggered by a certain valueAppearing a certain part of the computers memory, either relevant to the virusesPurposes or at random. The Trojan horse is an innocent seeming programPurposely infects with a virus and circulated publicly. There is a cure forThese viruses, though. These "cures" are called remedies. A remedy is aProgram that watches for typical things viruses do, halts them, and warns theComputer operator.