Mehler98
Aug 19th, 2009, 03:06 AM
Viruses are based on three ways a virus may add itself to the host code. These are: Shell virus, Add-On virus and Intrusive virus.
Shell virus: A shell virus is one that forms a shell around the original code. In effect the virus becomes the program and the original host program becomes an internal sub-routine of the viral code. When the virus has finished executing, it retrieves the host program code and begins its execution.
Add-On virus: Most viruses come under this category. These function by appending their code to the end of the host code or by relocating the host code and adding their own code to the beginning. The host code is left almost completely untouched. The only visible indication that a virus is present is that the has grown larger.
Intrusive virus: These operate by replacing some or all the original host codes with the viral code. The replacement might be selective as in replacing a subroutine with the virus or inserting a new interrupt, sector and routine. The replacement may also be extensive, when large portions of the host program are completely replaced by the viral code. In the latter case, the original program can no longer function.
Computer viruses are classified by their targets, the items they infect. These are:
Boot Viruses: Some viruses can “infect” disk by attaching themselves to special Web Design Services (http://www.intellixmedia.com/index.aspx) programmers in the areas of your disks called boot records and master boot records. These areas contain the programs your computer used to start up.
Program Viruses: These viruses infect executable files, such as word processing, spreadsheet, computer game or opening system programs.
Macro Viruses: In many word processing and spread sheet applications, you can record a macro that stores a series of actions. Later you can run the macro and automatically repeat the same actions. Macro viruses infect data files with macro capabilities. For example, MS Word document and template files and MS Excel spreadsheets are susceptible to macro virus attacks.
Shell virus: A shell virus is one that forms a shell around the original code. In effect the virus becomes the program and the original host program becomes an internal sub-routine of the viral code. When the virus has finished executing, it retrieves the host program code and begins its execution.
Add-On virus: Most viruses come under this category. These function by appending their code to the end of the host code or by relocating the host code and adding their own code to the beginning. The host code is left almost completely untouched. The only visible indication that a virus is present is that the has grown larger.
Intrusive virus: These operate by replacing some or all the original host codes with the viral code. The replacement might be selective as in replacing a subroutine with the virus or inserting a new interrupt, sector and routine. The replacement may also be extensive, when large portions of the host program are completely replaced by the viral code. In the latter case, the original program can no longer function.
Computer viruses are classified by their targets, the items they infect. These are:
Boot Viruses: Some viruses can “infect” disk by attaching themselves to special Web Design Services (http://www.intellixmedia.com/index.aspx) programmers in the areas of your disks called boot records and master boot records. These areas contain the programs your computer used to start up.
Program Viruses: These viruses infect executable files, such as word processing, spreadsheet, computer game or opening system programs.
Macro Viruses: In many word processing and spread sheet applications, you can record a macro that stores a series of actions. Later you can run the macro and automatically repeat the same actions. Macro viruses infect data files with macro capabilities. For example, MS Word document and template files and MS Excel spreadsheets are susceptible to macro virus attacks.