True, the most common issues are:
SPAM - I found that using SpamNet plugin for Outlook and Outlook Express in combination with my own rules in Outlook blocks 95% of the spam (I get about 250 spam messages a day)
VIRUS - Norton Anti-Virus is one of the best ones.
SPYWARE - Common sense works best - if you are browsing to a site and you get a popup for a permission to download something when you did not click on a download button, DON'T DO IT unless you know what that something is. For software that you do download and install, Norton Internet Security, ZoneAlarm and Outpost are very good for detecting outbound connections, though it can be a bit irritating. Outpost is pretty flexible about the rules. Ad-Aware should of course be run regularly to check for any Spyware that might have been installed (NOTE: NOT Adware is not the same thing as Spyware. Our software - QuoteTracker - is Adware, but we do NOT have any "Spyware" components that identify the individual users to advertisers)
POPUPS (web based) - There are lots of popup blockers out there. I frequently use NetCaptor browser which has popup blocking and ad blocking built in. Both Norton Internet Security and Outpost also have it built in (refer to SPYWARE above)
POPUPS (Microsoft System) - If you are connected to the net via a router such as Netgear or Linksys, or through a proxy server, you will not have that problem. If you connect direct, the firewall programs such as Outpost, ZoneAlarm and Norton Internet Security will block the messages, but the easiest thing to do is to disable the service in Windows (refer to the link in my previous post). Home users do not need that service anyway. This is only an issue on Windows NT, 2000 and XP computers.
Software referenced in this post (I am not affiliated with any of these companies):
Norton Internet Security
http://www.symantec.com/sabu/nis/nis_pe/
Outpost
http://www.agnitum.com/products/outpost/
ZoneAlarm
http://www.zonealarm.com
NetCaptor (great tabbed browser too)
http://www.netcaptor.com
Norton Anti-Virus
http://www.symantec.com/nav/nav_9xnt/ (NOTE: it may come together with Norton Internet Security as well)
SpamNet
http://www.cloudmark.com/products/spamnet/
Ad-Aware
http://www.lavasoftusa.com/software/adaware/
and of course
QuoteTracker, which I am affiliated with:
http://www.quotetracker.com