PoiNtEr->: Virus Programming Tutorial-2

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Saturday, September 22, 2012

Virus Programming Tutorial-2

A plethora of negative negative article about virus are available on internet.  Viruses are a result of very very clever programming.These bad articles are just creating a new kind of hypochondria among computer users: an unreasonable fear of computer viruses,and what Anti-virus manufactures are doing ?. Probably creating new ones .
Whatever get ready to understand the very basic structure of a virus.But before that a disclaimer :"The information contained in this post is for educational purposes only."

Functional Structure Of Virus
Every viable computer virus must have at least two basic parts, or subroutines, if it is even to be called a virus. Firstly, it must contain a search routine, which locates new files or new areas on disk which are worthwhile targets for infection. This routine will determine how well the virus reproduces, e.g., whether it does so quickly or slowly, whether it can infect multiple disks or a single disk, and whether it can infect every portion of a disk or just certain specific areas. As with all programs, there is a size versus functionality trade-off here. The more sophisticated the search routine is, the more space it will take up. So although an efficient search routine may help a virus to spread faster, it will make the virus bigger, and that is not always so good.

Secondly, every computer virus must contain a routine to copy itself into the area which the search routine locates. The copy routine will only be sophisticated enough to do its job without getting caught. The smaller it is, the better. How small it can be will depend on how complex a virus it must copy. For example, a virus
which infects only COM files can get by with a much smaller copy routine than a virus which infects EXE files. This is because the EXE file structure is much more complex, so the virus simply needs to do more to attach itself to an EXE file.
Virus Structure

Search, copy, and anti-detection routines are the only necessary components of a computer virus, and they are the components which we will concentrate in my next post.

Tools Needed for Writing Viruses
Viruses are generally written in assembly language. High level languages like Basic, C, and JAVA have been designed to generate stand-alone programs, but the assumptions made by these languages render them almost useless when writing viruses.They are
simply incapable of performing the acrobatics required for a virus to jump from one host program to another.

Compiler Choices
2:TASM(Borland’s Turbo Assembler)

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