Worms are very similar to viruses in that they are computer programs that replicate themselves and that often, but not always, contain some functionality that will interfere with the normal use of a computer or a program. Trojan horses are sometimes just called "Trojans" for short. Some people think of viruses as a special form of Trojan horse: one that can infect other files (thus turning them into Trojan horses) and duplicate itself.
#Get rid of worm virus software#
It is the generic term to refer to any software that is intentionally coded to do something other than what it is supposed to. The program doesn't necessarily infect other files or spread to other systems. What that all means, is that the virus can mutate in different ways to defeat virus scanners.Ī Trojan horse is any program that, once run, does something that the user doesn't want or request. In trivial form it simply adds randomly generated comments to randomly selected lines of virus source code.
#Get rid of worm virus code#
It may place part of the code at randomly selected locations, use different binary representations for each operation, etc. When such a virus infects a file, it uses those tables to generate a whole new polymorphic virus. The virus contains some encrypted tables describing which operations a virus take. Some new viruses use different approaches to be polymorphic. These viruses create a new decryption routine each time they infect, so every infected file will have a different sequence of virus code. A macro virus is often spread as an e-mail virus, or inside an infected document. A typical effect is the undesired insertion of some comic text at certain points when writing a line. Macro viruses tend to be surprising but relatively harmless. Most boot sector virus are also able to infect hard disks, where the process is similar to that described above, although they usually infect the master boot record instead of the DOS boot record.Ī macro virus is a computer virus that "infects" a Microsoft Office or similar application and causes a sequence of actions to be performed automatically when the application is started or something else triggers it. For example, a computer with 640K might appear to have only 639K.
A boot sector virus will usually hide at the top of memory, reducing the amount of memory that the DOS sees. Except, of course, that every diskette inserted in the computer will be infected with the virus, unless it is write-protected. It will then load and execute the original boot sector, and from then on everything will be as usual. When a computer is then later booted from this diskette, the virus takes control and hides in RAM.
The virus replaces the original boot sector with itself and stores the original boot sector somewhere else on the diskette or simply replaces it totally.
On diskettes, the boot sector normally contains code to load the operating system files. In addition to this general virus definition there are several types of virus, you can read a description of the main types below :īoot sector virus infects boot sectors on diskettes and/or hard disks. Computer viruses often infect many programs on the same system or even parts of the operating system in an attempt to spread themselves as far as possible. Recommendations about Viruses What is a virus ?Ī computer virus is a type of computer program that is designed to hide in the background and replicate itself from one computer to another by attaching itself to existing programs or parts of the operating system.