You can try grc.com if you want to max out your paranoia level: the site provides some good tools for testing your firewall and seeing if you have any ports open. Combined with a proper external firewall/router (if you're on broadband) and not just the Windows firewall, a good, up-to-date virus checker and an anti-spyware tool and you're a very long way to ensuring that your PC is safe.
There are simple checks you can do too - is your PC continually working (eg. the hard drive chattering) even when you're not doing anything? Is the modem light constantly flickering as traffic passes through even though you've got no applications running? Does the machine continually run slow?
A lot of these zombies are running unpatched machines with broadband connections and no firewall. They are usually in the hands of home users with little technical knowledge.
I have often wondered where the proxies I buy come from :)
Only half a joke, that ;) When you see lists of "anonymous proxies" floating around, they are often misconfigured home machines rather than real servers.
That isn't as clear a sign as you might think - Hard disks will chatter when recalibrating due to thermal expansion. Other things like pagefile access or Windows "findfast" updating an index will light up your hard drive.
Msg#: 8142 posted 10:57 am on Mar 19, 2005 (gmt 0)
All such useless background nonsense should be disabled. I've only ever been caught by one virus, but it was hard disk activity that gave it away within seconds of my system becoming infected. Total infection time, a few minutes - I rebooted in another version of Windows and blasted that virus into oblivion.