What is the difference between a virus and worm?

I've google searched it and I find contradicting definitions. According to wikipedia "A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer" which makes it sound like all viruses are file infectors. Then I go to the article on computer worms and it defines it as a "self-replicating malware computer program" but it just said viruses can spread.

So not all viruses are file infectors, right?

They both affect files..

A virus spreads from computer to computer via humans.. in other words, someone sends an email with a virus to another person.. or copies a file on one computer and takes it to another... etc.

A worm, on the other hand, doesn't rely so much on humans... it can spread from computer to computer on its own... through the network or internet.

Unless you're a professional security expert conversing with another professional security expert, I don't think the difference in meaning between virus and worm and spyware and adware is significant. They are all bad if they end up on your computer, and as a user you won't really care what it's called, you'll just want to know how to get rid of it and how to prevent it from returning. I like the term 'malware' myself which covers all the unwanted crapola that may get on a computer.

To me discussing the semantic content of the terms 'virus' vs. 'worm' is similar to a bunch of programmers sitting around arguing if zero is a positive or negative number. Kind of a waste of time imho.

Please bare with me I'm trying to make a point!

According to hiker
So does that mean that there are no standalone .exe that are malicious code? All viruses and worms append there code to a host file and are executed when the host is run?

A virus is a program that is designed to spread from file to file on a single system, it does not intentionally try to move to another system, and it must replicate, and execute itself to be defined as a virus.

A worm is designed to copy itself (intentionally move) from PCto PC, via networks, internet etc.

A worm doesnt need a host file to move from PC to PC, whereas a virus does.

So worms spread more rapidly then viruses.

Virus and Worms both are dangerous for the PC.

Viruses are bad but worms in my experience have been a scarier beast. Only once has my network had a worm. I caught it almost immediately. I had some av software I was paying for (Norton at the time?) and it didn't catch it. I saw it in the logs for a server I had runing a tarpit. I was running a /24 network and was using maybe 15 IP addresses. All the rest had open connections to the infected computer and the tarpit server. Since my AV didn't catch it, I just wiped the computer. I don't play around with infections since all my important goodies are safely backed up.

Anyways, avoid both

What worms are most dangerous nowadays?

As of October 12, 2010, here are the 10 Most Destructive Computer Worms and Viruses Ever

Hi!
What is a virus?
A virus is a computer program those copies themselves from one computer to another. A Virus is not a program itself but is computer code that is written into a legitimate document or program. Once this document or program is launched the code begins to run on your computer. Once a computer has a virus it can do various things including deleting data, and can interrupt the computer's operating system so that it will no longer run. Viruses are often spread by email, either by someone forwarding an infected document to another user or by self-propagating. A self-propagating virus automatically sends email to everyone in the infected computer's email address book. For Lotus Notes users, this is generally not the case. Most self-propogating virus's are writtent to utilize the Microsoft Outlook email technology, not Lotus Notes. Virus's can also be spread from computer to computer via networks.

What is a Worm?
A computer worm is much common a virus but does not require any help from a person to circulate. Computer worms circulate from computer to computer via networks. Worms exploit holes in operating system security so it is important to download and install all patches.
Thank You.