Viruses- Types and Examples

Computer Security

A virus acts on a computer just like it acts on the human body. When the human body gets a virus it is usually treated by a doctor and when the computer gets a virus, it too has to be treated. Again, comparing a computer to the human body, there are various types of viruses that can attack and each one has to be treated differently.

There are many types of viruses and depending on what the virus is and which part of the computer gets attacked will depend on how to repair it. You should be familiar with the different types so at the very least, you can identify that there is indeed a problem and address it. The first is called a boot virus. This type of virus attacks the floppy disc boot records and replaces the boot record program. Major problem here! This is the program that is responsible for loading the operating system in memory. It either copies everything on the disc and puts it somewhere else or just overwrites it.

Program viruses are the ones that infect executable program files. These are generally the ones that have extensions such as .BIN, .COM, .EXE, .OVL, .DRV, and .SYS. Upon execution these programs are loaded into memory and take the virus right along with it. Once it becomes active, it replicates itself and infects the files on the disc.

Multipartite viruses are a combination of the boot and program viruses. They infect the program files and when the infected program is executed, the virus will infect the boot record. The next time that you boot up the computer the virus that is in the boot record loads up in memory and spreads like a wildfire through the computer.

Stealth viruses apply certain disguises so that they are not easily detected. They could redirect the disk head to read
another sector besides the one that they are supposed to be reading or intersperse the reading of the infected file's size that is shown in the directories listing. One example is the Whale virus which adds 9216 bytes to an infected file.

Polymorphic viruses can encrypt its code in various ways so that it looks different in each infection. This type is much more difficult to detect. Macro viruses are fairly new and they infect the macros within a template or a document. What occurs when you open a word processing program, the virus is activated and infects the NORM.dot. This is where the default document formatting settings are stored. Every single file that you open gets infected as soon as you open it. This virus then attaches itself to the documents and spread to any place that the document is opened, even on another computer.

Finally, Active X and Java, these are the viruses that will terrorize the computers in the future. This is a growing problem because most people do not know how to manipulate their web browsers by enabling or disabling most of the functions, hence leaving a nice section open for invasion. Although this is a vague coverage of what type of viruses are prominent, it may also help you in the future to protect your computer from harm.