Well, be that as it may.
This box isn't carrying any viruses, Norton A/V makes sure of that, I've never found any malware when I run Spybot S&D and I use Zonealarm Pro in addition to the routers integral firewall.
I feel confident that this obsolete, promiscuous, venereal disease threatened machine is safe. I'm the only one who ever touches it so I know where it's been.
... the routers integral firewall ...
This is your most potent defense against worms and port probers. Make sure that you have the latest firmware on your router, though. Firewalls on routers aren't invincible. Periodically, there are holes found -- and hackers *will* find you if you don't apply the firmware patch. Same deal with software firewalls. Stay up to date -- or you're toast.
Regarding Spybot, etc: The newest forms of malware are getting very, very smart about the kinds of damage that they do. Many of them are actively hiding from and altering programs such as Spybot, Ad-Aware, ZoneAlarm, Norton, etc so that they don't get reported. So, while you may think that you're safe, you may not be. It's a constant arms race between malware producers and spyware detectors. Your best bet is to simply use caution when you use your computer. Don't download and run software from an unverified source; if you must, run it with a lower privilege (not Admin). Don't install ActiveX controls. Don't use HTML mail. Turn off scripting. Don't visit malware-oriented websites (ie. p0rn, war3S, hacx0rz, etc).
One very easy (and most often overlooked) thing that people can do is to download a new HOSTS file (see
Blocking Unwanted Parasites with a Hosts File and (
Skallas' Ad Blocking Hosts file). The nice thing about this approach is that it works on practically EVERY operating system in use (Windows, Mac OS X, Linux, etc). This makes it easy to redirect known bad sites to 127.0.0.1 (your own machine). So your browser, when it sees references to IMO bogus sites like doubleclick.net, won't even hit the network at all. It will ignore those entries. Depending on the content of HOSTS, this has the added advantage of blocking a lot of ad traffic -- which makes your browsing experience more pleasant (heh heh).