| Computer Virus What are Viruses? The definition of a computer virus is a software program that attaches itself to another program in computer memory or on a disk, and spreads from one program to another. Viruses may damage data cause the computer to crash, display messages or lie dormant. What are the different types of viruses? There are many different type of viruses that can infect your system in this section I will explain the differences between virus types. MASTER BOOT RECORD/BOOT SECTOR INFECTOR A Master Boot Record (MBR)/Boot Sector virus infects the system's Master Boot Record on hard drives and the Boot Sector on floppy diskettes. This type of virus takes control of the system at a low level; activating between the system hardware and the operating system. A MBR/Boot Sector virus is loaded into memory upon boot-up, before virus detection code can be executed. MACRO VIRUS Some computer applications contain macro languages to help automate tedious tasks. As computers have grown more powerful, the tasks have become more complex and so have these languages. Some macro languages offer the ability to write into files other than the original document. This feature may be used by virus authors to create unwanted macros, which "infect" documents. If the resulting macro can continue to infect, it matches the general virus definition ("replicates and infects"). Known Macro viruses infect and are spread through Word Documents. MULTIPARTITE A virus that infects Master Boot Records, Boot Sectors and Files. POLYMORPHIC A virus that attempts to evade detection by changing its internal structure or its encryption techniques. Polymorphic techniques use some system of changing the "form" of the virus each infection in order to avoid detection by signature scanning antiviral software. Less sophisticated systems are referred to as self-encrypting. SPAWNING A viral program that does not actually attach to another program, but which uses a similar name and the rules of program precedence to associate itself with the regular program. This kind of virus is also referred to as a Companion Virus. STEALTH Various techniques used by viruses to avoid detection. Examples of techniques used by Stealth viruses: 1. Redirecting system pointers and information in order to infect a file without actually changing the infected program file. 2. Another Stealth technique is the ability to hide an increase in file length by displaying the original, uninfected file length. TROJAN HORSE A program that either pretends to have, or is described as having a (beneficial) set of features but which, either instead or in addition, contains a damaging payload. Most frequently the usage is shortened to Trojan. Trojan Horses are not viruses. They do not replicate. Home |