Windows Rehab 101

2. Lock It Down
The good news: Because you won´t be surfing the Web or getting e-mail on this PC, it´s unlikely to get infected by spyware or a computer virus. Your wireless router has a built-in network address translator (NAT) that hides your IP address from attackers, making it hard for some cyberstranger to plant a remote-access Trojan or other zombie-ware on the hard drive.
The bad news? There might be some evildoers lurking on that hard disk already. And if your wireless network hasn´t been secured, some digital delinquent could camp outside your house with a Wi-Fi-powered laptop and hitch a free ride on your broadband connection-or worse, steal your data.

Scan your system. Several security-software firms, including BitDefender, Panda Software and Trend Micro offer free online virus and spyware scans. In many cases you´ll need to use Internet Explorer and download an Active X applet to run the scan. If the scan finds anything, you usually have to buy software to get rid of it. (Look for products that offer 30-day free trials, so you can cancel before you have to pay.)

Turn on the firewall. A software firewall adds an extra layer of protection, making your computer completely invisible to outside attacks. To turn on the one built into XP, click Start, select Control Panel, and launch the Network Connections applet. Under the Network Tasks column, select â€Change Windows Firewall settings.†Put a check mark next to â€On (recommended),†click â€OK,†and close the Network Connections app.
Windows 2000 doesn´t have a built-in firewall, but you can download a free one from Sunbelt Software or ZoneLabs. Just launch the setup software and follow the prompts.

Turn off file sharing. This will keep other people who manage to sneak onto your network from snooping around your system´s hard disk. In XP, launch My Computer, right-click on the drive letter, and select Sharing and Security. If you´ve installed XP Service Pack 2, file sharing should be turned off by default. If not, make sure the box next to â€Share this folder on the network†does not have a check mark in it. For doing the same in Windows 2000, see this page.

Secure your Wi-Fi network. You can keep strangers from logging on to your wireless network or even knowing that you have one, but the exact steps will vary depending on the kind of router you have. Start by opening up your Wi-Fi router´s settings page-you can usually get there by opening your browser and typing http://192.168.0.1 or http://192.168.1.1 into the address window (some routers may use a different address, so check the manual). You´ll have to supply a username (typically â€admin†if you haven´t changed it) and password (often â€password†or â€publicâ€; for a long list of default names and passwords, see this page). From there you can change your default username and password, tell your network to stop broadcasting its service set identifier, or SSID-essentially your network´s name-or turn on encryption/password protection. Without your SSID or your password, drive-by hackers won´t be able to log on (but if you forget them, neither will you, so write them down).
For more on Wi-Fi security and drive-by hacking-also known as wardriving-see wardrive.net.

Award-winning journalist and proto-geek Dan Tynan is author of Computer Privacy Annoyances (O´Reilly Media, 2005).