no firewall? Check this out:
Jacques wanted to show me just how risky it is to connect an unprotected PC to the 'net. We set up a poor Windows XP machine with no firewall or anti-virus software - connecting it to the Internet would be like throwing it into a lion pen with raw meat strapped to its hard drive. How long would it be before we were hit by something nasty on the net? Hours, minutes? As it turned out - eight seconds!
We were hit by Sasser, one of the fastest spreading worms on the 'net, and it wastes no time at all in taking over your PC. Within seconds of infection, our PC started downloading some strange programs, or payloads, from mysterious Internet addresses. These payloads are the programs that can take control of your machine and turn it into a remote controlled bot.
Our machine then started scanning random Internet addresses, looking for other vulnerable PCs to infect. Then Internet Explorer started downloading spyware. Within 5 minutes our PC was running so many malicious programs, that the CPU was running flat-out at 100% - and we weren't even touching it.
http://www.bbcworld.com/content/clickon...ive_14_2005.asp?pageid=665&co_pageid=3
Keep in mind that article was written in April so things might be even uglier now.