The Common Types of Computer Virus

The Common Types of Computer Virus

Boot viruses

 The boot record program loads the operating system in the memory at startup. These viruses replace the boot record and move it to a different part of the hard disk, or simply overwrite it. To avoid loading the boot record viruses into memory, you must boot your operating system from another source .

Program viruses

These types of computer virus will infect only executable files  Once executed, these programs load into memory, along with the virus contained within them. Once in the memory, the scenario repeats – the virus is free to act and infect other files or simply deliver its payload. These viruses are friendlier than boot viruses and can be removed a lot easier.

Multipartite viruses

These computer viruses are hybrids, derived from boot viruses and program viruses. They infect executable files, just like the program viruses but, once the executable is executed, it infects the master boot records. The scenario is similar to the boot virus’s one: once you boot your operating system, the virus is loaded into the memory, from where it is free to infect other programs and replicate itself, ultimately delivering the payload.

Stealth viruses

These viruses are specialized in avoiding detection and will use a number of techniques to do so. Most of them simply redirect the hard disk head, forcing it to read another memory sector instead of their own. Some of them also alter the reading of the file size shown when listing the directory. These types of computer virus are very hard to find by humans, but antivirus software is specially designed to track them down and erase them.

Polymorphic viruses

The polymorphic viruses will always change their source code from one infection to another. Each infection is different, and this makes detection very hard. However, detection is still possible, depending on the antivirus.

Macro viruses

This virus is relatively new and it infects macros within a template or document. When you open a word processing document, it activates the virus. The virus infects the Normal.dot template, which is a general file used by all the documents. So, whenever you open an uninfected document, by referring to the Normal.dot file, it gets infected as well. This infection can only spread if infected documents are opened on another machine.

Active X viruses

Most people do not know how to configure ActiveX and Java controls, unconsciously leaving a security hole. Applets are then allowed to run freely on the machine, delivering all ActiveX viruses. By simply turning off some ActiveX and Java controls in the browser, a user can efficiently protect their PC from this type of computer virus.