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Types of Computer Viruses

In computing terminology, a ‘malicious code’ is a term used for computer viruses and programs designed to cause damage to computers. Other types of destructive PC worms are known as Internet virus including the examples like Worms and Trojans.

Outlined below is the description of different kinds of computer viruses:-

Program/File Infector: Falling under the category of parasitic viruses, a program or file infector attempts to infect the files with extension code like .exe, .com, .drv, .dil, .bin, .ovl, and .sys. It gets activate along with the execution of executable file containing virus. The virus then loads itself into memory and replicates itself to other executable files when these files are opened or run.

The File Infector virus can destroy the content contained in files and cause irreversible damage to them. Some file viruses have also operated as email worm and Trojan horse.

The best way to disinfect files infected by the file virus is to delete them and restore from back up.

Macro Computer Virus: A macro computer virus is a virus written in a language built into a software application such as a word processor. For example: Microsoft Office has the macro language built into its application. This is why most of its application programs are affected by macro computer virus.

Macro viruses are generally created using the macro recorder or Visual Basic for Applications. The applications that are the most prone to this virus are Word Documents, Excel Spreadsheets, Power Point Presentation, and Access Database. The virus infects templates of these documents and therefore every file that the user opens gets affected. Some common macro computer viruses are Auto Exec, Auto New, Auto Open, Auto Close, and Auto Exit.

The auto macros can be disabled by using the command ‘DisableAutoMacros’ in any macro that is written. Another way to remove it is by holding down the shift key while opening a document.

Multi-Partite Virus: It behaves in the same way as other computer viruses do. As the name signifies, they are sometimes more than one type. These are hybrids and are known as multi-partite virus.

Polymorphic Viruses: It is a kind of virus which produces different but operational copies for itself. Its attack is considered to be extremely dangerous as virus detectors will not be able to detect all instances of virus attacks simultaneously. And this is one of the reasons why it is known to be strategically designed.

Stealth Viruses: A stealth virus uses different mechanisms to prevent recognition by antivirus software. It tries to escape detection either by redirecting the disk head to head to read another sector or modifying the file size shown in the Directory listing.
Classification of some viruses is not possible as they are the file type viruses which start behaving as computer worms with an activation code.