What is a computer virus?

Question

Ok, we all know that a virus invades your computer and damages stuff.
But that stuff? And how does it gets into your computer when you doenload it or something?
Basically how does it work?
Also, how are viruses made?

Thank you!

Answer 1

Virus:

A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.



Spyware:

Spyware is computer software that is installed surreptitiously on a personal computer to intercept or take partial control over the user's interaction with the computer, without the user's informed consent.



Adware:

Adware or advertising-supported software is any software package which automatically plays, displays, or downloads advertising material to a computer after the software is installed on it or while the application is being used. Some types of adware are also spyware and can be classified as privacy-invasive software.



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Answer 2

A computer virus is a program or unwanted software that spreads by first infecting files or the system areas of a computer or network router's hard drive and then making copies of itself. It can cause lots of damage to the targeted device.. So, it's important to keep our devices safe and secured from these worms with the help of some various efficient tools available in market known as Antivirus software... There are many antivirus software that can help you in this matter and serving as great precaution since long time... The antivirus software that you can get online are Avast, Microsoft Security Essential, Optimo Defender, Bit Defender, Avira, etc,..

Answer 3

2

Answer 4

There are many different types of viruses.



The most common type is called a trojan.

These viruses can do anything from monitor your computer, to stealing your files, to destroying your computer from the inside out.

The only way, for now, to get a trojan onto your computer is to download it, and run it.



For example, have you ever downloaded a '.exe' file, and when you try to open it, it asks if you want to run it, that's 'cuz it might be a virus.



There are also other viruses that you can get just from going to an un-secure web site. These are less damaging, usually, but can be very strong, compromising your computer's security in a number of ways.



A virus can be made in a number of ways.

if you open notepad and type



@echo off

shutdown -s



and save it as something.bat

when someone runs it, it will turn off their computer.



scripts that are just annoying, doing things like opening many different programs can also be written in notepad.



this will open a bunch of files



@echo off

start:

call omg.bat

start notepad

start calc.exe

goto start



if you download a folder, and open this program,

it will start notepad and calculator, and open a file called omg.bat, which could do a number of things, and it will keep on doing it.

opening omg.bat, notepad and calculator

until you close the program.



viruses are just programs that use common computer tasks to gain un-authorized access to files and personal information, and for some people, to be rude and annoying.

Answer 5

A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, adware, and spyware programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer



The term "computer virus" is sometimes used as a catch-all phrase to include all types of malware. Malware includes computer viruses, worms, trojans, most rootkits, spyware, dishonest adware, crimeware, and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with computer worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself to other computers without needing to be transferred as part of a host, and a Trojan horse is a program that appears harmless but has a hidden agenda.

Answer 6

A virus can damage anything on your PC, depending on what is was programmed to damage, from blackening out your screen, to frying your hard-drive. Viruses are malicious codes that are programmed to do bad things to computers. They usually lurk in downloads and e-mail attachments.

Answer 7

viruses can enter your pc from many sources...email, websites, attachments to software, chat rooms (IM), etc.



viruses replicate and spread just like a person catches a cold or virus



some viruses are destructive and delete or corrupt files and others are just nuisances

Answer 8

What is a virus?



A virus is a program that can infect or contaminate other programs and is often detrimental to computer data or system integrity. Viruses are most frequently spread by opening infected email attachments. The virus can then send itself to everyone listed in the recipient's email address book. Some viruses are spread through Internet downloads, while others are spread through infected disks. There are thousands and thousands of known viruses, and new virus strains continue to show up regularly. The rate of virus infection is rapidly increasing.



History of computer viruses



A program called "Elk Cloner" is credited with being the first computer virus to appear "in the wild" -- that is, outside the single computer or lab where it was created. Written in 1982 by Rich Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread by floppy disk. This virus was originally a joke, created by the high school student and put onto a game. The game was set to play, but release the virus on the 50th time of starting the game. Only this time, instead of playing the game, it would change to a blank screen that read a poem about the virus named Elk Cloner. The computer would then be infected.



The first PC virus was a boot sector virus called (c)Brain, created in 1986 by two brothers, Basit and Amjad Farooq Alvi, operating out of Lahore, Pakistan. The brothers reportedly created the virus to deter pirated copies of software they had written. However, analysts have claimed that the Ashar virus, a variant of Brain, possibly predated it based on code within the virus.

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of the personal computer, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk.



Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS and modem use, and software sharing. Bulletin board driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBS's. Within the "pirate scene" of hobbyists trading illicit copies of commercial software, traders in a hurry to obtain the latest applications and games were easy targets for viruses.



Since the mid-1990s, macro viruses have become common. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Excel. These viruses spread in Microsoft Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS, most of these viruses were able to spread on Macintosh computers as well. Most of these viruses did not have the ability to send infected e-mail. Those viruses which did spread through e-mail took advantage of the Microsoft Outlook COM interface.



Categories of viruses



File-Infecting Viruses

This is the most common type of virus. A file-infecting virus attaches itself to an executable program file by adding its own code to the file. An executable program file can be run and has an .EXE extension. The virus code is usually added in such a way that it escapes detection. When the infected file is run, the virus can attach itself to other executable files. Files infected by this type of virus usually have a .COM, .EXE, or .SYS extension. Damage to data can occur when the virus is triggered. A virus can be triggered when an infected file is executed, or when a particular environment setting is met (such as a specific system date).



Boot-Sector Viruses

When a computer boots (or starts), it looks to the boot sector of the hard disk before loading the operating system or any other startup files. A boot-sector virus is designed to replace the information in the hard disk's boot sectors with its own code. When a computer is infected with a boot-sector virus, the virus' code is read into memory before anything else. Once the virus is in memory, it can replicate itself onto any other disks that are used in the infected computer.

Trojan Horse Programs



Trojan horses

As a legitimate program such as a game or utility, but once it is executed, it can destroy or scramble data. A Trojan horse program can contain viruses, but is not a virus itself.



Worms

A worm is an independent program that replicates itself, crawling from machine to machine across network connections. It often clogs networks as it spreads, often via e-mail.



How do viruses spread?



Viruses are most frequently spread by opening infected email attachments. The virus can then send itself to everyone listed in the recipient's email address book. Some viruses are spread through Internet downloads, while others are spread through infected disks.



How can i prevent computer viruses?



You must buy and run quality software on all your computers to protect you from viruses, spyware, and other potentially harmful applications. There is no budget solution, you must do the following or it is likely your computer will be hit by a virus and your work/data will be lost:



Get good anti virus software e.g. one of the below.

Regularly update your 'virus definitions' e.g. once per week.

Email Attachments: BEWARE OF ATTACHMENTS. Do not open email attachments that you are not expecting. Viruses come with some very nasty messages to trick you into opening the attachement e.g. "Your email account has been cancelled, see attachment for details". Even worse, the virus looks like it comes from an email address you recognise e.g. from [e-mail] (where 'your domain' is the domain name that you use). Virus attachments tend to have the following 'file extension': .exe, .pif. If you receive a .zip attachment and open it - make sure it doesn't contain a file with one of those extensions. Do not open attachments you haven't requested, even if they appear to be from people you know.