What are the Types of Computer Viruses?

Computer viruses are generally defined as a program inputted into a computer that allows replication of the program installed. As it replicates, the program intentionally infects the computer, typically without even the user knowing about the damage being done. A virus, unlike worms or Trojan horses, needs an aid to transfer them to computers. Viruses usually take a large amount of computer memory, resulting into system crashes. Viruses are categorized to several parts based on its features.

Macro Viruses

A macro virus, often scripted into common application programs such as Word or Excel, is spread by infecting documents. Macro viruses are known to be platform-independent since the virus itself are written in language of the application and not the Operating System. When the application is running, this allows the macro virus to spread amongst the operating systems. There are thousands of macro viruses that exists, and each are considered major threats. Examples of these viruses are: Melissa.A and Bablas. pc.

Network Viruses

Network viruses rapidly spreads through a Local Network Area (LAN), and sometimes throughout the internet. Generally, network viruses multiply through shared resources, i.e., shared drives and folders. When the virus infects a computer, it searches through the network to attack its new potential prey. When the virus finishes infecting that computer, it moves on to the next and the cycle repeats itself. The most dangerous network viruses are Nimda and SQLSlammer.

Logic Bombs

The logic bomb virus is a piece of code that are inputted into a software system. When a certain and specific condition is met, such as clicking on an Internet browser or opening a particular file, the logic bomb virus is set off. Many programmers set the malicious virus off during days such as April Fools Day or Friday the 13th. When the virus is activated, then various activities will take place. For example, files are permanently deleted.

Companion Viruses

Companion viruses takes advantage of MS-DOS. This virus creates a new file with typically the .COM extensions, but sometimes the .EXD extension as well. When a user manually types in a program they desire without adding .EXE or any other specific extention, DOS will make the assumption that the user want the file with the extension that comes first in alphabetical order, and thus running the virus. The companion virus is rare among Windows XP computers as this particular operating system does not use the MS-DOS.

Boot Sector Viruses

Boot sector viruses generally hide in the boot sector, either in the bootable disk or the hard driv

e. Unlike most viruses, this virus does not harm the files in the hard disk, but harm the hard di sk itself. Boot sector viruses are uncommon at this day and age because these v iruses are spread rapidly by floppy disks and not on CD-ROMs.

Multipartite Viruses

Multipartite viruses are spreaded through infected media and usually hides in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects executable files on the hard drive and later across the computer system.