On 09.10.06, In When I was young, when somebody says that their computer is affected with virus, I used to think, as I got virus fever, the computer too got infected by the same type of virus. But it is different, of course.
Computer Virus is a kind of malicious software written with the only intention of entering into others computer without the permission of the owner or user of that computer. Not only permission, even without their knowledge. These viruses have ability to replicate themselves and keep spreading from files to files, disks to disks, drivers to drivers.
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The most common types of viruses are:
Boot Virus: The favorite job of this virus is to affect the boot sector of a floppy or hard disk. This sector is a very crucial part of a disk, where all the information about the disk itself is stored together, along with a program which makes it possible to boot (start) the computer from the disk. Few examples of this type virus are Polyboot.B, AntiEXE.
Companion Virus: Companion virus is either can be a direct action virus sometimes or can be a dependent virus sometimes. That is, it can carry out the infection work by its own sometimes, and along with other viruses like resident viruses at times. The name companion came, as it accompanies some other viruses at times. Few examples are Stator, Asimov.1539, and Terrax.1069
Direct Action Virus: This is a batch file, which always finds a place in the root directory of the hard disk. This master mind carries out operations when the computer is booted. It replicates itself and infects the files in its directories as well as other directories, which are mentioned in the AUTOEXEC.BAT file path.
Directory Virus: This virus will move your files from their location you stored them and they will get stored quietly in your files location, with the same name. It is like the villain of a movie replaces himself in the place of hero, after kidnapping the hero. Without knowing the truth, when you try to execute the file, the hidden virus will show its face, laughingly. After this, you can never locate your original (kidnapped) files.
FAT Virus: The file allocation table or FAT is the part of a disk which contains all information about the files and their allocations. It has a vital role in the normal functioning of the computer. The FAT virus attack may prevent you from accessing the certain sections of the disk where important files are stored.
File Infectors: The very common virus normally found in computers. They infect the executable files more than ordinary program files.
Logic Bombs: They are not considered as virus as they do not replicate. Also, they are not programs. They are rather classified as camouflaged segments of other programs. Their motto is to destroy data on the computer once certain conditions have been met. Logic bombs go undetected until launched, and the results can be destructive.
Macro Virus: Macro virus affects the applications / programs that contain macros. Macros are mini-programs, which helps the users to perform a lots of actions in a single shot, instead of doing one by one. Few examples of macro viruses are Relax, Melissa.A, Bablas and O97M/Y2K.
Overwrite Virus: This virus will just delete the contents / information of your original files and overwrite them with its own infected code, making the files useless to you. You will left with only one choice of deleting those infected files, and lose your original too. Few examples of this virus are Way, Trj.Reboot, Trivial.88.D.
Polymorphic Virus: This is a super mind virus, which can encrypt or encode itself using different algorithms and encryption keys, every time it wants to infect a system. So, even the anti-viruses get confused and cry that they couldn’t catch this virus. Few Examples of polymorphic virus are Elkern, Marburg, Satan Bug, and Tuareg.
Resident Virus: This virus happily takes the permanent resident ship in the RAM memory, and loves to interrupt all works of the operating system, corrupting the files and programs when they are opened, closed, renamed or copied. Few examples are CMJ, Meve, MrKlunky, Randex.
Trojans or Trojan Horses: Those who know the story of Troy will know what Trojan horse means. This virus will hide themselves inside other files and will act when time comes. They don’t infect files like other virus, nor do self-replication like worms. They quietly sit in your computer, reading all your work and entries (like passwords) and loyally report to the head quarters.
Worms: A worm is also a program like virus, with an extra ability to self-replicate, just like the worms replicate in a decayed food. So, how does a spoiled food smells? Your computer will also be like that once when a worm enters in. Few examples of worms are PSWBugbear.B, Lovgate.F, Trile.C, Sobig.D, Mapson.
Some people seem to have a lot of time to develop these viruses and spread them on the net…
Thanks for posting this article. very informative!
Quite informative and advanced information about viruses.
Frightening things. good article that throws light on all kinds of viruses.
All kinds of spyware comes with freeware. We need to be careful.
@Uma Not all, there are a lot of innoncent content developers that don’t add spyware. That’s why you get an anti-virus such as Avast.
Nice overview of what computer viruses are all about. It is sad how some people try to hurt other people via their computers.
great post, very informative
Very informative..Thanks for sharing about this
hmm very helpful info since i don’t quite understand what type of viruses did my Anti Virus caught when it writes it in the report.