What is the differences between a virus and a worm?

Answer 1

All the answers given so far are WRONG. :-(

BTW, asking this question at a convention of computer anti-virus researchers is a sure-fire way to start a fight. :-)

Seriously, there is no agreement on this subject. There are three main different schools of thought.

According to the first one (the one I also subscribe to), a worm is a kind of virus that *explicitly* uses the network to replicate itself. Note the emphasis on the work "explicitly". For instance, a virus which just enumerates all drives and infects the files on them might spread over the network if one of those drives happens to be a mapped network drive - but this doesn't count as "explicitly". Also, the kind of network doesn't matter - it could be e-mail, TCP/IP, WiFi, Bluetooth, anything.

According to the second school of thought, a worm is again a kind of virus - but one which is self-contained, i.e., which does not attach itself (infect) other executable files. That doesn't necessarily mean that it consists of a single file - it could consist of a set of several files; the important thing is that it doesn't infect other files. Personally, I prefer to call such viruses "non-parasitic", as opposed to the parasitic ones - i.e., the ones that infect other files. Furthermore, there are viruses that do not infect files (e.g., boot sector viruses, companion viruses, etc.) which, historically, have not been considered worms. While it could be argued that most of those are at least in some way "associated" with a host (even if they don't physically attach themselves to it), there are some members of these types of viruses that would work even if the "host" is absent - yet they aren't called "worms", either.

According to the third (and most exotic) school of thought, a viruses and worms are two different kinds of malicious programs (i.e., worms aren't viruses). In addition, a worm must be able to spread without any human interaction whatsoever - i.e., it has to be able to self-instantiate itself on the remote computer. According to this definition, CodeRed is a worm - but LoveLetter is not ( because the latter requires the user to click on an e-mail attachment).

The reason for this disagreement is because the term "worm" first gained wide popularity when the Morris Worm was released in 1988. That particular worm was a "worm" according to all of the above definitions; but people disagreed which of its properties made it a worm (instead of a simple virus).

Answer 2

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Answer 3

a virus corrupts your files and a computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computer terminals on the network) and it may do so without any user intervention. Unlike a virus, it does not need to attach itself to an existing program. Worms always harm the network (if only by consuming bandwidth), whereas viruses always infect or corrupt files on a targeted computer.

Answer 4

What Is a Computer Virus

Computer viruses are actually small programs that have the ability to replicate themselves and then spread throughout your system in many ways. This is usually done without a user’s knowledge. Such programs may copy themselves to a shared network resources or mail themselves to E-Mail Contacts that are stored in your address book.

After a Virus has infected your system, it will usually trigger itself in some sort of fashion. It can launch annoying pop up windows that repeatedly place messages on your screen. It can deny you access to your data files and even change your system configuration settings. In advanced stages of infection, a virus can cause major damage to your system as it can corrupt your files and render them unreadable. It can even start deleting files as well. A virus doesn’t always have to trigger itself upon infection. It can actually be programmed to launch at a specific time or on a specific date so that there will be no obvious sign of system infection. A virus will usually disguise itself and may even attach itself to another file, so as to trick a user into running it.

Worms And Trojan Horses

A Worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well. The term worm was coined by John Brunner, a science fiction writer, in his 1975 novel Shockwave Rider. The hero, a talented programmer, created self-replicating computer programs that tunneled their way through a worldwide network.

A Trojan Horse is simply a malicious computer program that damages your computer system upon installation. The program claims to do one thing, such as pretending to be a game, but instead do something else when you run them. Some nasty Trojans will actually attempt to erase your hard drive. They were originally named after the historic Trojan horse used by the Greeks to conquer Troy because the first Trojan horse programs pretended to be innocent games or applications. Trojan horses have no way to replicate themselves automatically. Below you will find some of the various ways that viral related attacks can be transmitted and spread.

Answer 5

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Answer 6

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Answer 7

Virus doesnot allowed your program to run properly,where worms spoils your hard drive.

Answer 8

in short terms
a virus harms your pc and files
a worm can affect other pc's thru yours as it spreads
i.e. email worms etc,,,