if you have an updated linux installation, then there is currently no known virus in the wild that will affect you...
there have been a few linux viruses/worms in the past, but they relied either on some security bugs (which were quickly fixed), or on a retarded system administrator...
there are many reasons why linux isn't subject to the same virus threats that windows users are so used-to, but the reasons will vary depending on who you ask...
it's an endless discussion... this question is very popular, partly because it's one of the first questions most windows power users ask when trying linux for the first time... they are so used to the daily virus nightmares on windows, so they suppose it's something
normal and to be expected on any OS...
here's an article that might be
interesting to you:
http://www.theregister.co.uk/2003/10...ndows_viruses/
also, as for general security issues (which worms usually take advantage of) you can look at the top 20 security issues for windows and linux and come to your own conclusions:
http://www.sans.org/top20/
spyware... well, it would be VERY strange to get spyware bundled with open-source software, as any programmer would be able to see the spy code and blow the whistle on it... so as long as you only install software from trusted sources, you won't have to worry about bundled spyware...
as for getting spyware from surfing the web, if you use a decent browser (such as
firefox), which you can configure to
not install anything from the web, you shouldn't have any issues either...
there's a few linux antivirus products out there, but as i said earlier, there isn't any current threat if you're updated and only install trusted software packages...
if you're worried about sending infected files to windows users, there's an open source antivirus called clamav that's pretty neat:
http://www.clamav.net
keep in mind that those files that are infected with windows viruses would generally be harmless on your linux machine, you're just scanning them to protect the windows machine where the file will be opened...
i'd imagine that when linux becomes more popular on the desktop, clamav will also scan for linux
malware, but i'm not sure, though...
