Computer Notes Chapter -11 Computer Virus ! Virus ! What is Computer Virus ! How viruse may affect files ! What viruses may do to a computer ! Detecting Viruses ! virus myths !

Computer Virus 

Virus :

 

One of the biggest fears among new computer users is being infected by a computer virus or programs designed to destroy  their personal data. Viruses are malicious software programs that have been designed by other computer users to cause destruction and havoc on a computer and spread themselves to other computers where they can repeat the process. 

A computer virus is a software program that was first written Rich Skrenta in 1982 who was 15-year old high school student. Known as the Elk cloner this virus spread to other computers by monitoring the floppy drive and copying itself to any floppy diskette that was inserted into the computer. Once a floppy diskette became infected it would infect all other computers that disk was inserted into, each computer that was infected would then infect every floppy diskettes inserted it. A computer that was infected would also display a short poem on every 50 booth.

Computer users can help protect themselves against computer viruses, malware, and computer security threats by installing and antivirus protection program. 

What is a Computer Virus ?

  A computer virus is a software program that has been intentionally created to cause a user grief, spread to other computers, or destroy data on an individual's computer. To help prevent a computer from becoming infected by a virus, software developers have developed antivirus programs that stay active on the computer helping to protect it. it  is important to realize that many computers do not come per-loaded with these already and that if computers do come with these programs, the programs may expire within 90 

1. Viruses can affect any files: however, usually attack.com, .exe, .sys, .bin, pif, or any data files.

      Viruses have the capability of infecting any file: however, will generally infect executable file or data files, such as word or excel documents that are opened requently and allow the virus to try infecting other files more often.

2. Increase the files size, however this can be hidden. 

      When infecting files, virtues will generally increase the size of the file: however, with more sophisticated viruses these changes can be hidden .

3. It can delete files as the file is run.

     Because most files are loaded into memory, once the program is in memory the virus can delete the file used to execute the virus.

4. It can corrupt files randomly.

      Some destructive viruses are not designed to destroy random data but instead randomly delete or corrupt files.

5. It can cause write protect errors when executing .exe files from a write protected disk .

      Viruses may need to write themselves to files that are executed: because of this, if a diskette is write protected, you may receive a write protection error.

6. It can covert .exe files to .com files.

      Viruses may use a separate file to run the program and rename the original file to another extension so the exe is run before the com.

7. It can reboot the computer when executed.

     Numerous computer viruses have been designed to cause a computer to reboot, freeze, or perform other tasks not normally exhibited by the computer.

What Viruses may do to a computer?

    Below are possibilities you may experience when you are infected with a virus. Remember that you also may be experiencing any of the below issues and not have a virus.

1. Deleted files.

2. Various messages in files or on programs.

3. Changes volume label.

4. Marks clusters as bad in the FAT.

5. Randomly overwrite sectors on the hard disk.

6. Replaces the MBR with own code.

7. Create more than one partition .

8. Attempts to access the hard drive, which can result in error messages such as: invalid drive                        specification.

9. Causes cross-linked files.

10. Causes a "sector not found" error.

11. Cause the system to run slow.

12. Logical partitions create, partitions decrease in size.

13. A directory may be displayed as garbage.

14. Directory order may be modified so files such as COM files, will start at the beginning of the directory.

15. Because Hardware problems such keyboard keys  not working, printer issues, modem issues etc.

16. Disable ports such as LPT or COM ports.

17. Caused keyboard keys to be remapped.

18. Alter the system time/date.

19. Causes system to hang or freeze randomly.

20. increase files size.

21. Increase or decrease memory size.

22. Randomly change the file or memory size.

23. Extended boot times.

24. Increase disk access times.

25. Cause computer to make strange noise, make music, clicking noises or beeps.

26. Display pictures.

27. Different types of error message.

Detecting Viruses :

  The recommended method of detecting and cleaning the computer from any computer viruses or other malware is an antivirus protection program  

Alternatively, a user can look at various aspects of the computer and detect possible signs indicating a virus is on the computer. while this method can used to determine some viruses, it cannot clean or determine the exact virus you may or may not have and is not recommended.

Virus myths:

 

 Below are come comments we've come across that common misconception when it comes to computer viruses and other. malware.

1. "If download a file onto a disk, I don't have to about a viruses."

     This is not true, just because you have placed a file on a diskette or moved a file from a diskette to your hard drive does not mean that your computer cannot be infected. Many viruses are memory resident and capable of loading themselves into memory once a diskette is placed in the computer.

2. If buy sealed software i don't have to worry about virus." Or "If i just buy registered software i don't have to worry about viruses.

 This is not always true, just because the program may be surrounded in  plastic doesn't mean that it cannot be infected with a virus. When a software program is saved onto a diskette or disc if that computer or program is infected the virus will attach itself. Although this issue very rarely occurs it is still a possibility .

3. "If I don't download anything off of the internet I don't have to worry about viruses ."

    This is definitely not true. Although most companies and web sites will scan the  files for viruses before they make them available to download some may not. in addition many people create a site or a file to download with the intention of spreading a virus, spy ware, Trojan horses, or other malware.

4. "If I just read my e-mail, I will not have to worry about viruses."

 Not true: there are viruses out there that are distributed through e-mail; also files can be attached with e-mail and if executed can infect the computer. Today this is one of the most common ways computer viruses spread around the world.

5. "If I don't on the internet I don't to worry about viruses."

    This, Unfortunately, is not the case. Although many viruses are spread over the internet today it is still possible to contact a computer virus form any diskette or disc you put in the computer. 

6. "You can contact viruses from just looking at web pages."

Not  true. However, you can contact a viruses if you download and execute a file from that web page. in addition spy were and other scripts can be executed from just viewing a web page. Although these programs are not designed to delete files on your computer they should be considered a privacy violation.