If you think a firewall is just a nusiance and your antivirus software is enough, think again. There is more t worry about that you think. Check out this recent log from my router:

Mon, 2008-09-08 13:38:27 - UDP Packet - Source:80.50.125.22,18935 Destination:71.167.195.160,19550 - [DOS]
Mon, 2008-09-08 13:38:27 - UDP Packet - Source:90.217.215.227,26881 Destination:71.167.195.160,19550 - [DOS]
Mon, 2008-09-08 13:38:28 - UDP Packet - Source:86.137.255.127,56107 Destination:71.167.195.160,19550 - [DOS]
Mon, 2008-09-08 13:40:24 - UDP Packet - Source:4.79.142.206,137 Destination:71.167.195.160,137 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,4 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,5 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206 Destination:71.167.195.160 - [PORT SCAN]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,0 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,1 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,2 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,3 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,4 - [DOS]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206 Destination:71.167.195.160 - [PORT SCAN]
Mon, 2008-09-08 13:40:55 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,0 - [DOS]
Mon, 2008-09-08 13:40:56 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,2 - [DOS]
Mon, 2008-09-08 13:40:56 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,3 - [DOS]
Mon, 2008-09-08 13:40:56 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,4 - [DOS]
Mon, 2008-09-08 13:40:56 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,5 - [DOS]
Mon, 2008-09-08 13:45:56 - TCP Packet - Source:4.79.142.206 Destination:71.167.195.160 - [PORT SCAN]
Mon, 2008-09-08 13:50:56 - TCP Packet - Source:4.79.142.206,59055 Destination:71.167.195.160,0 - [DOS]

This is only reflecting 20 minutes of activity, but in that short time my PC was under attack from 4 different hackers. 3 of them were attempting a Denial of Service attack on my network while another was doing a port scan, trying to find an open port to use to hack into my system. Throughout the day there are thousands of these entries recorded, as the bad guys use automated programs to bombard the net, looking for a target. Luckily, because of my firewall, none of the attacks get anywhere-but if you have a wireless or wired network set up and no firewall, you've basically thrown your front door open to the net inviting the bad guys in. So make sure you have a firewall-and while you're at it, make sure your network uses WEP encryption and change those usernames and passwords-every router is sold with the defaults of admin and password, and the bad guys know it!