Computer Viruses
Essay Preview: Computer Viruses
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A computer virus is a simple set of computer instructions or code that is written by some unscrupulous person. This code is attached to some part of the normal computer operating system or computer program. Instructions in this code tell the computer to perform some task. This task is often destructive, such as deleting important information or crashing the hard disk. There are other that may be only a slight aggravation. Some viruses have been known to do nothing more than put a large happy face on your computer screen (Berger).
There are different types of viruses that can infect different parts of system. Some viruses are harmless that a computer user might not notice for years. 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. Another type of virus is a program virus. This virus infect executable program files, such as those writing extensions like .BIN, .COM, .EXE, .OVL, .DRV [driver and .SYS [device driver]. These programs are loaded in memory during execution, taking the virus with them. The virus becomes active in memory, making copies of itself and infecting files on disk. Examples of this type of virus are Sunday and Cascade. Multipartite viruses are hybrid of Boot and Program viruses that infect program files and when the infected program is executed, these viruses infect the boot record. When you boot the computer the next time the virus from the boot record in the memory starts to infect other program files on disk. Examples of these types of viruses are Invader, Flip, and Tequila.
Stealth viruses use certain techniques to avoid detection. It may either redirect the disk head to read another sector instead of the one which reside or they make alter the reading of the infected files size shorter than the directory listing. For instance, the Whale virus adds 9216 bytes to an infected file; than the virus subtracts the same number of bytes (9216) from the size in the directory. Examples of this type of virus are Frodo, Joshi, and Whale. Polymorphic viruses are a virus that can encrpy its code in different ways so it appears differently in each infection. These viruses are more difficult to detect. The names of some of these viruses are Involontary, Stimulate, Cascade, Phoenix, Evil, Proud, and Virus 10. Macro viruses are a new type of virus that infects macris within a document or template. When you open a word processing spreadsheet document, the macro virus is activated and it infects the Norm template (Normal.dot) a general purpose file that stores default document formatting settings. Every document you open refers to the Normal template which gets infected with the macro virus. Since the virus attaches itself to documents, the infection can spread if such documents are open on other computers. Some names of these viruses are DMV, Nuclear, and Word Concept. (Mayur Kamat Viruses-Types and Examples).
Do your ever wonder why people write and spread viruses? It is difficult to know why people do them when everyone has their own reason. Some general reasons are to experiment how to write viruses or to test their programming talent. Some people just like to see how the virus spread and gets famous around the World. The main mission viruses have is to spread out and then get active. Some viruses just spread out and never activate and when they spread out they make copies of its self. How viruses spread out? They join the host program in some way and then write over the part of the host program (Hanhisalo).
People wonder what be the signs of a computer virus. Almost anything odd a compute may do, can blamed on a computer “virus,” especially if no other explanation can readily be found. Many operating systems and programs also do strange thing, therefore there is no reason to immediately blame a virus. In most cases, when an anti-virus program is then run, no virus can be found. A computer virus can cause unusual screen displays, or messages but something it dont do that. A virus may slow the operation of the computer but many times that doesnt happen (Hanhisalo). The trigger activates the virus can be almost anything. For instance, the virus can be activated the minute it is installed. On the other hand, it may initiate its dirty work the next time you start your computer (Berger).
Symptoms of viruses, worms, and trojan horse viruses:
If you suspect or confirm that your computer is infected with a virus, obtain current antivirus software. When a virus infects your e-mail or other files, it may have the following effects on your computer:
The infected file may make copies of itself. This may use all the free space in your hard disk. A copy of the infected file may be sent to all the addresses in your e-mail address list.
The virus may reformat your disk drive and delete your files and programs. The virus may install hidden programs, such as pirated software. This pirated software may then be distributed and sold from your computer. The virus may reduce security. This could allow intruders to remotely access your computer or network.
The following symptoms are frequently caused by or associated with a virus:
You received an e-mail message that has a strange attachment. When you open the attachment, dialog boxes appear or a sudden degradation in system performance occurs. There is a double extension on an attachment that you recently opened, such as .jpg.vbs or .gif.exe. An antivirus program is disabled for no reason and it cannot be restarted. An antivirus program cannot be installed on the computer or it will not run. Strange dialog boxes or message boxes appear onscreen. Someone tells you that they have recently received e-mail messages from you containing attached files (especially with .exe, .bat, .scr , and .vbs extensions) that you did not send. New icons appear on the desktop that you did not put there, or are not associated with any recently installed programs. Strange sounds or music plays from the speakers unexpectedly. A program disappears from the computer, but you did not intentionally remove it (Computer Viruses).
When you find out you have a virus on your computer the first thing you need to do is count to ten and stay calm. You should also keep notes on what you do, write down what your virus programs, and your computer tells you. If you are not sure what to do, you should call the administrator for future action. In some cases it is not good