Just a general question as to how a traditional virus works... if the virus infects a piece of executable code, then i suppose it gets executed along with the exe. But what about the older type virus which live on floppy disks? I remember they used to say that as soon as you access the disk drive, they will "jump" onto your system, even if you don't execute anything. How does that actually occur? How does that piece of code get run, if nothing is executed? Very confusing... =)

Okay, a virus is a sort of unclear term. It is used differently by different people. In this context, we will assume a virus is code dependent on an external process for execution. A worm would be code that requires no external process for execution (though it most certainly will exploit something external). A virus is code whose chief purpose is to copy itself (and maybe do something malicious along the way). To do this, it needs to get into an execution stream. The virus can get itself called by adding a line to a configuration script, appending itself to files which are to be opened (and maybe processed), or getting the OS or a process to run it through an exploit. Scripting which allows user priveleges to be waivered (like in Windows) is ideal. In your floppy example, a passive read is not an execution (under most circumstances - auto-detection and some other things play with this). Therefore I would term a malicious code that is proactive in that context as a worm. A virus requires an existing execution process, which will allow it opportunity to infect and spread. Think of how a real-world virus infects the body - it is fairly passive until it reaches its target and begins reproduction. Some individuals believe worms are a type of virus.

Worms are smart viruses that can infiltrate and replicate themselves on systems. Unlike most virus which may just be executed thru a file click, worms can infiltrate your pc by going thru holes in your software, without you actually clicking or downloading anything. Most worms do not actually do the type of damage a virus can do. Lots of worms just mail themselves all over using your address book and can be just an annoyance. Viruses can do very serious damage to your pc. Mind you, i am not saying that worms are not bad, nimda was not fun. I'd have to say worms are evolved viruses, most virus code is easy to write, and specifically defined to a particular task like deleting your c:\windows without asking. However most worms evolve and can be built to improve themselves. Have a look at the history of nimda ... hope that helps