Types of computer virus

Types of computer viruses:

• Boot viruses
• Program viruses
• Macro viruses
• Companion viruses
• Worms
• Trojan horse
• Adware
• Spyware

Let us discuss one by one:

1. Boot Viruses:

Boot viruses infect only the master boot records (MBR) of the hard disk. This would make the computer either unable to boot or booting would take place along with virus code. All this would lead to the spread of virus attack to disks being used with the computer.

2.Program Viruses:

 Program viruses infect only executable programs. Once executed, programs load into memory, along with the virus contained within them. Once loaded into memory, now virus can infect other application programs and disks being used thereby corrupting data or making it useless.

3.Macro viruses:

Macro viruses affect programs and document . This infection can only spread if infected documents are opened on another machine, eg., affecting the default template (normal.dot) of word thereby stopping any edit or save operations etc.

4.Companion Viruses:

This virus attaches itself with existing files.When infected file runs, the virus gets activated and can affect other program/files.

5.Worms Virus:

A worm is a special type of malicious program that keeps replicating and hence end up eating all the storage of the computer.

Worms are autonomous agents capable of propagating themselves without the use of another program or intervention or action by a user. Worms are found primarily on computers that are capable of multitasking and are connected by a network.

Most worms disrupt services and create system management problems. Some worms scan for passwords and other loopholes and then send the information back to the attacker. In some case worms can install Trojan horses or viruses that cause damage to the systems.

6.Trojan horse:

A trojan horse is code hidden in a program such as a game or spreadsheet that looks safe to run but has hidden side effects.

When the program is run, it seems to function as the user expects, but in actuality  it is destroying, damaging, or altering information in the background. It is a program on its own and does not require a host program in which to embed itself.

An example of a Trojan horse would be a Christmas executable that, when executed, pops up with an animated figure of Santa Claus and a caption saying "Merry Christmas". In the background, extra code could be deleting files or performing other malicious actions.

Trojan horses are generally spread through e-mail and exchange of disks and information between computers. Worms could also spread Trojan horses.

The damage that Trojan horses cause is much the same as what a virus causes. Most of the time users are unaware of the damage it is causing because of the Trojan horse's masking effect.

8.Adware:

Adware is a form of malware. Adware is designed to pop up advertisements. Adware can be very annoying.

9. Spyware:

Spyware is written to monitor actions on a computer. A common type of spyware is key-logger program. This program can record every key stroke and mouse click you make.

Hope you learnt something from this article...

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