Viruses, Trojans, Worms & Types

 Virus 
           

(a)        A Computer virus is a software program designed to function in a manner diametrically opposed to legitimate software.

(b)        It will load and run without a request. To meet the minimum criteria for computer virus design, a program must be executable, be capable of cloning itself and converting other executable objects into viral clones. Hence, it may be a simple DOS batch file.

Types of Virus           There are six types of Computer viruses

                (a)    Boot Sector Infectors (BSI)  
                (b)    Command Processor Infectors (CPI) 
                (c)    General Purpose Infectors (GPI)       
                (d)   Multipurpose Infectors (MPI)
                (e)    File specific Infectors (FSI)   
                (f)    Memory Resident Infectors (MRI).

Boot Sector Infectors            Computer viruses that specialize in altering data in the master boot sector are called BSIs. They are loaded immediately upon system start up, before the command processor loads and of course before any anti-viral program can be loaded 

Command Processor Infectors        CPIs affect the hidden files as well as the command processor the COMMAND.COM file. These viruses have the advantage of examine a large majority of the interaction between the user and the computer.

General Purpose Infectors        GPIs are designed for the broadest range of infections compatibility. They infect any or particular executable files. They adapt well to most executable file formats, moving quickly among files

Multi Purpose Infectors         MPIs are designed to combine some or all the infectious tributes of the BSIs, CPIs and the GPIs. They are a potent, adaptable and deadly combination of computer virus technologies.

File specific Infectors            FSIs target a fixed number and fixed type of files. FSIs are viral cruise missiles, programmed to seek out and destroy the intended target files and property.

Memory Resident Infectors        MRIs could be boot sector or command processor infectors. They are always loaded and active.