I have been using Linux continuously for 4 years and have never once been infected with a virus, trojan, or adware. It simply doesn't happen. However, I have seen unmaintained machines get hacked. Like any software, you need to stay current to stay safe. Debian has an excellent security record, and it includes a great tool for software updates (apt). You should also learn what services your machine is running and why, and turn off the ones you don't need.
If you're completely new to Linux, you might want to check out one of the bootable CD distros like Gnoppix. You can download/buy a single CD that boots directly into a Debian-based desktop, without modifying your existing system. Gnoppix has very good autoconfiguration, possibly easier to use than what's currently available in Debian stable. -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]