Network Stumbler lets you save your war-driving information in a file, and you can then upload that information to a web site (such as http://wifimaps.com) that uses your information and information provided by many other war-drivers to create maps of WiFi networks across the country. You can zoom in and out on these maps, so you can get a view of the concentration of WiFi networks in a metropolitan area, or you can see individual WiFi networks on individual streets, as shown in Figure 7-4.

Figure 7-4. A map of WiFi networks in my neighborhood

Go to http://wifimaps.com to view the maps or to upload your Network Stumbler information. Be aware that the site is a volunteer effort, and, not uncommonly, you’ll find the maps aren’t working. If that happens, check back again in a few days; it usually gets up and running after a while.

One way to increase the range of your war-driving and the strength of the signal when you connect to WiFi networks is to build your own wireless antenna. You can build one for a few dollars using a tin can and other stray parts, as long as you’re willing to do a little bit of soldering. Because they’re built out of tin cans, they’re frequently called cantennas.

My 15-year-old son, Gabe, built several for his seventh-grade science fair project several years ago and compared the effectiveness of each. The results were clear: the giant 34.5-ounce coffee cans were far superior to normal-size coffee cans and Pringle’s cans.

If you haven’t bought a WiFi card yet and are considering building one of these cantennas, I suggest buying an Orinoco card. It has a small connector in its side through which you connect a pigtail connector, which can then be hooked up to a small antenna you build out of copper wire and a small connector, which goes inside the tin can. You can buy a pigtail and the required connectors at a number of places, including HyperLink Technologies (http://www.hyperlinktech.com). If you don’t have a WiFi card with a small connector, building one of these cantennas becomes much more difficult.

You can find good directions for making cantennas at numerous web sites. Three good places to start are http://www.oreillynet.com/cs/weblog/view/wlg/448, http://www.netscum.com/~clapp/wireless.html, and http://www.turnpoint.net/wireless/cantennahowto.html. Just so that you get the idea of how to build one, though, I’ll give you an overview here. First you empty and wash the can. Next, you build the small antenna that will go inside the can by soldering a short piece of thick copper wire to a small piece of hardware called an N connector. Then, drill a hole in the can and insert the small antenna you just soldered. Attach the antenna to the can by securing it with small screws and bolts. Attach one end of the pigtail to your wireless card, attach the other end to the N connector, and voilà! You have a cantenna.

Your service set identifier (SSID) is your network’s name, and if people know what your SSID is, it’s easier for them to find your network and connect to it. Your router broadcasts its SSID, and that broadcast tells passersby there’s a network there. It also gives out the name, which makes it easier to connect to.

So, if you turn off SSID broadcasting, you’ll go a long way toward protecting your network. But doing that, by itself, won’t necessarily solve the problem. Even if you stop broadcasting your network’s name, people might still be able to connect to your network. That’s because manufacturers generally ship their wireless routers with the same generic SSID; for example, Linksys routers all have the SSID “Linksys” by default. So, even if you stop broadcasting your SSID, intruders can easily guess your router’s name and log on.

The answer? First change your SSID’s name, and then hide it. That way, passersby won’t see it, and they won’t be able to guess it either. How you do this varies from manufacturer to manufacturer, and even from model to model from the same manufacturer. But for many models of Linksys routers, here’s what to do.

To change your SSID name and stop broadcasting it, log in to the setup screen by opening your browser and going to http://192.168.1.1. When the login screen appears, leave the username blank. In the password section type admin, and then press Enter.

Click the Wireless tab and look for the Wireless Network Name (SSID) box. Enter the new name of your network. On the same screen, scroll down to SSID Broadcast and choose Disabled, as shown in Figure 7-7. Then, click Save Settings. If you are doing this from a wireless PC, you will immediately lose your connection to the access point and the Internet.

Figure 7-7. Changing your SSID name from the default

After you change your network name, reconnect each WiFi computer to the network, using the new network name. To reconnect in Windows XP SP2, right-click the small wireless icon in the Windows system tray. From the screen that appears, click Change Advanced Settings, and then click the Wireless Networks tab. Click the Add button in the Preferred Network section, type the network name, click OK, and then OK again. In installation of Windows XP prior to SP2, click the small wireless network icon in the Windows system tray and select the Wireless Networks tab. Click the Add button, type in the network name, click OK, and then OK again.

While you’re at the Wireless screen, there’s something else you can do to help keep your network invisible to outsiders. You should regularly change the channel over which your router transmits. That way, if someone has tapped into it before, she won’t know on which channel it’s now broadcasting. Choose a new wireless channel from the Wireless Channel drop-down list, and then click Save Settings.

Your wireless router uses DHCP to hand out network addresses to each PC on your network. So, another way to stop intruders from hopping onto your network is to limit the number of IP addresses it hands out to the number of computers you actually have. That way, no one else will be able to get an IP address from your network’s DHCP server because your PCs will use up all the available IP addresses.

Your router’s built-in DHCP server hands out IP addresses whenever a computer needs to use the network, and the router lets you set the maximum number of IP addresses it hands out. To limit the number on a Linksys router, go to the Setup screen and scroll to the bottom. In the Number of Address box, type the number of computers that will use your network and click Save Settings, as shown in Figure 7-8. If you add another computer to your network, make sure you go back to the screen and increase the number of DHCP users by one.

Figure 7-8. Limiting the number of IP addresses your DHCP server hands out

If you use this technique, you’ll also have to change the number of IP addresses your router hands out if you turn off one of your PCs or take it away from the network. For example, if you take a laptop with you on the road, remember to change the number of IP addresses your router hands out and decrease the number by one.

The simplest way to check if you have an intruder is to see a list of every PC on your network. If you see an unfamiliar PC, it means you have an intruder.

To see all the computers currently on your network and their MAC addresses, log on to the router, click Status, and then click Local Network. Click the DHCP Client Table button, and you’ll see a list of all the PCs on your network, their IP addresses, and their MAC addresses, as shown in Figure 7-9. If you see an unfamiliar computer listed there, you have an intruder. To kick the intruder off the network, check the box next to its listing and click Delete.

Figure 7-9. Checking to see whether any intruders have made it onto your wireless network

That will only temporarily solve the problem, though. The intruder can simply reconnect to your network and get a new IP address. You can, however, permanently ban any specific PC from ever connecting.

When you see an intruder, write down his MAC address. Then click Security, and from the screen that appears click Edit MAC Filter Setting. From the MAC Address Control Table that appears, type the MAC address onto a line and click Apply. The PC with that MAC address will now be permanently banned from your PC.

For even more security, you can allow only PCs with certain MAC addresses onto your network—just those who you want to let in. How you do this varies from router to router, but on a Linksys, from the main setup screen choose Wireless → Wireless Network Access to get to the Wireless Network Access screen. Select Restrict Access. Scroll to the bottom of the screen and click Wireless Client MAC List. You’ll see a list of every wireless PC on your network, including their MAC addresses. Check the Enable MAC Filter box for each computer and click Save. You’ll be sent back to the Wireless Network Access screen, and the MAC addresses of each PC will be put in a box next to MAC 01, MAC 02, and so on. Click Save Settings. Now, only computers you specify will be allowed onto your network.

If you want to allow a new computer with a different MAC address onto your network, you need to add that MAC address. To find out the computer’s network adapter’s MAC address, at a command prompt type ipconfig /all and press Enter. The screen will display information. Look for the numbers next to Physical Address, such as 00-08-A1-00-9F-32. That’s the MAC address. Copy that number into a MAC box on the Wireless Network Access screen, and that computer will be allowed to connect to your network. When you copy the number, don’t include the hyphens.

Your router keeps logs that track all the activity on your network. So, if you regularly check those logs, you can find out whether you’ve been targeted, or whether an intruder has made his way onto your network.

How you check the logs varies from router to router. But on many Linksys routers, you can examine both your incoming and outgoing logs. Log on to the router, click Administration, and then click Log. You’ll see two buttons: Incoming Log and Outgoing Log.

Click Incoming Log to display a screen that shows the most recent inbound traffic, including the source IP where the traffic is coming from and the destination port number on a PC on your network. It’s tough to decipher this screen, and there’s not much immediately useful information here. Much more useful is the Outgoing Log, which shows all outbound traffic. It shows the LAN IP address of each piece of originating traffic, as well as the destination and the port number used. If you see unfamiliar destinations and LAN IP addresses, you have an intruder.

These two screens provide only a current snapshot of your network use, and they don’t provide immediately useful information. But there’s downloadable software that examines your router logs in much more detail and which can give you much useful information, including whether you’re under attack, where the attack is coming from, the type of attack you’re under, and similar information.

The best of the bunch is shareware, rather than freeware. Link Logger (http://www.linklogger.com) works with routers from Linksys, Netgear, and ZyXEL. When you run it, it automatically gathers information from your router logs, monitors your network, reports on what exploits and weaknesses are being targeted, and provides a wide range of reports and graphs. If you do find you’re being attacked, it will list the attacker’s IP address and computer name and identify the ports on his PC where the attack is coming from, as well as the IP address, computer names, and ports on your network being attacked, as shown in Figure 7-10. It will also specifically identify the type of attack.

Figure 7-10. The Link Logger Reports screen

So, for example, you can create a report, like the one shown in Figure 7-10, which lists for you all the attacks and alerts over a given period of time and includes a breakdown of the number of each type of attack.

You can also use Link Logger to try to get back at your attackers, by asking that their ISPs investigate them and possibly take action against them. First you need to find out the attacker’s ISP. Then, send an email to the ISP and include the log files in the message.

On the Link Logger main screen, scroll until you find an attack or group of attacks from the same person, as shown in Figure 7-11. (Each attack will have an icon of a skull and crossbones next to it.) Do a Whois search, which will match the IP address with its ISP. Then, do an ARIN Whois Database Search at http://network-tools.com by typing the IP address into the box near the bottom of the screen and pressing Enter.

Figure 7-11. Using Link Logger to find out the IP address and other information identifying an attacker

You’ll see the name and contact information for the ISP, as shown in Figure 7-12.

Figure 7-12. Using this site to find out the attacker’s ISP and to send the ISP an email, including the Link Logger log

Most of the time, it will also include an email address for the person you should contact if you discover you’ve been attacked by someone who uses the ISP. Often, it’s an address such as [email protected]. (This is the address that would appear if the attacker uses the Comcast ISP.)

Now that you have the right email address, you need to send an email to it and paste log information into the email. Right-click the listing or group of listings that originated the attack and choose Copy. That will copy the log information to the Windows Clipboard. Paste the information into an email, and send it to the ISP of the attacker.

Despite all your precautions, there’s a chance that someone has broken into your network, or at least uncovered information about it. People who go war-driving [Hack #65] often tell the whole world about unprotected WiFi networks they’ve found. So, there’s a chance that information about your network is listed on a publicly available web site, for all the world to see. If so, someone can use that information to try and get into your network.

First, you need to find out the MAC address of your router. It’s often listed on one of your router’s screens, but if you don’t know it, it’s easy to find. To find it, first go to the command line and ping your router’s IP address. You’ll find it in your router documentation. For a Linksys router, the IP address is 192.168.1.1. So, for a Linksys router, at the command line type the following and press Enter:

ping 192.168.1.1

Strictly speaking, you don’t need to ping the router. But it’s a good idea to do it because when you ping it, the router’s MAC address information will be put into your PC’s Address Resolution Protocol (ARP) cache. Then it’s easy to grab the information out of the cache.

After you ping your router, stay at the command prompt, issue the following command, and press Enter:

Arp -a

A screen like the one shown in Figure 7-13 will appear. Your MAC address will be listed directly under Physical Address.

Figure 7-13. Finding out your router’s MAC address

Now that you know your router’s MAC address, you can see whether information about your router is posted on a public web site. Go to http://www.wigle.net. Click the Search link on the lefthand side of the screen. You’ll have to register at the site, but it’s free, so before you search for your MAC address, fill out the registration information.

Once you’ve registered, log in, and the screen shown in Figure 7-14 appears. In the BSSID or MAC box, type in the MAC address of your router, making sure to put colons between the numbers, instead of the hyphens that Arp shows you. For example, you would type in a MAC address like this:

00:0b:db1c:7b:3b

Figure 7-14. Checking the WiGLE web site to see whether a wireless network has been “outed”

Click Query. If a blank screen comes up, information about your network hasn’t been posted to the site. But if your network is there, there will be a great deal of information about it, including its SSID, the channel it is broadcasting on, and other identifying information.

If your network is found, you should take quick action. Use the techniques in this hack and also turn on wireless encryption [Hack #69] .

To use WEP encryption, you must configure your router to use it, choose an encryption key, and then configure all your wireless network adapters to use the encryption with the proper key.

First, go to the Setup screen of your router. For a Linksys router, open a browser, type http://192.168.1.1 in the address bar, and press Enter. A login screen appears. Leave the “User name” field blank; in the Password field, type admin and press Enter. If you’ve changed the username and password, use those instead.

From the Setup screen, choose Wireless → Wireless Security. Select Enable next to Wireless Security. The Wireless Security options, which will have been grayed-out when you came to the page, will now be live so that you can fill them out.

Select WEP from the Security Mode drop-down list. In the Default Key section, choose any key from 1 through 4. (It doesn’t matter which you choose.)

Next, select the wireless encryption level you want to use. You have a choice of 64 bits or 128 bits. Using 128-bit encryption is much more secure than 64-bit encryption, although it will slow down your network to a certain extent. Businesses should absolutely use 128-bit encryption, and home users should consider using it as well, despite potential network slowdowns. But before choosing 128-bit encryption, make sure your WiFi adapter supports it. Some WiFi adapters support only 64-bit WEP encryption. Check your documentation or the manufacturer’s web site for details.

From the Wireless Encryption Level drop-down box, choose either “64 bits 10 hex digits” or “128 bits 26 hex digits.” Depending on which you choose, the form you have to fill out will change, as illustrated in Figures Figure 7-15 and Figure 7-16.

Figure 7-15. Using 64-bit WEP encryption rather than 128-bit (for WiFi network adapters that don’t support 128-bit encryption)

Figure 7-16. Choosing 128-bit WEP (a better bet than 64-bit because of its increased security, despite slight network slowdowns)

If you chose 64-bit encryption, type a phrase in the Passphrase box and click Generate. That will generate the WEP key you’ll use on your router and each PC on the network. Four keys will be created in the WEP Key boxes. You’ll use only one of these keys at a time, but you generate four of them because you can manually switch between them at regular intervals, for added security. You don’t have to generate your keys this way; you can create them yourself and type them in manually. But, chances are, it will be far easier to crack than one randomly generated by the router’s software, so it’s a good idea to use one the router will create for you.

If you instead selected 128-bit encryption, you’ll be sent to a new screen. In the Passphrase box, type a phrase and click Generate. This will generate a 128-bit encryption key.

Regardless of whether you created a 64-bit key or a 128-bit key, copy the key (or keys, in the case of 64-bit) onto a piece of paper. You’ll use this key for each PC that is going to access the network.

Click Save Settings. That applies the key to your network. From now on, only PCs that use WEP encryption and the key you just generated will be able to get onto your network.

Now that you’ve configured your router to use WEP, you have to configure each wireless computer on your network to use WEP and the key you just generated. On each PC, click the wireless connection icon in the system tray. Then, click Properties, click the Wireless Network tab, highlight your network, click Properties, and then click the Association tab. The dialog box shown in Figure 7-17 appears, although it won’t yet be filled out.

Figure 7-17. Choosing the right key number for 64-bit encryption

In the Network Authentication drop-down box, select Shared. In the Data Encryption dialog box, choose WEP. When you do that, the box that reads “The key is provided for me automatically” is checked. Uncheck this box.

Enter your WEP key in the “Network key” box and type it again in the “Confirm network key” box. From the Key Index, choose the key number that you’ll be using. Click OK and then OK again. Now the PC can connect to your network using WEP encryption.

For added security, change the key number and associated network key on each PC regularly. You shouldn’t need to change the number on your router because it will recognize all the keys you generated. If you use 128-bit encryption, you’ll have only one key to use.

The process for turning on WPA encryption is similar to that for turning on WEP, with a few differences along the way. First, you need to make sure your version of XP supports WPA. SP2 does; earlier versions don’t. To check whether you have SP2 installed, right-click My Computer, choose Properties, and look on the General tab. If you have SP2 installed, it will tell you at the bottom of the System section near the top of the tab.

If you don’t have SP2, go to http://www.microsoft.com/downloads/details.aspx?FamilyId=009D8425-CE2B-47A4-ABEC-274845DC9E91 and download a system patch that will install WPA on your system. Or, you can update your entire system to SP2 by going to http://windowsupdate.microsoft.com.

Now that your system supports WPA, you need to make sure all your hardware supports it as well, by checking the documentation and manufacturers’ web sites. If not, see if firmware updates are available, and download and install them. Remember, you’ll have to upgrade your router and wireless networking adapters, not just a few components. Also download the latest driver for your network adapters.

Once your system and hardware are WPA-enabled, go to the Setup screen of your router. For a Linksys router, open a browser, type http://192.168.1.1 in the address bar, and press Enter. A login screen appears. Leave the “User name” field blank; in the Password field, type admin and press Enter. If you’ve changed the username and password, use those instead.

From the Setup screen, choose Wireless → Wireless Security. Select Enable next to Wireless Security. The Wireless Security options, which will have been grayed-out when you came to the page, will now be live so that you can fill them out.

Select WPA Pre-Shared Key from the Security Mode drop-down list. In the WPA Algorithms drop-down list, choose TKIP, which is the approved, certified algorithm for WPA. Some products support Advanced Encryption System (AES), but that hasn’t been certified for interoperability among different vendors’ hardware.

In the WPA Shared Key box, type a key between 8 and 63 characters in length. The longer it is and the more random the characters, the more secure it will be. Write down the key. You’ll need to use this on each wireless PC on your network.

Leave the Group Key Renewal row at 3600. Click Save Settings. That applies the key to your network. Figure 7-18 shows what the screen should look like when you’re done. Now, only PCs that use WPA encryption and the key you just generated will be able to get onto your network.

Figure 7-18. Creating a long and random WPA shared key for a more secure network

Now that you’ve configured your router to use WEP, you have to configure each wireless computer on your network to use WEP and the key you just generated. On each PC, click the wireless connection icon in the system tray. Then, click Properties, click the Wireless Network tab, highlight your network, click Properties, and then click the Association tab.

In the Network Authentication drop-down box, select WPA-PSK. In the Data Encryption dialog box, choose TKIP. When you do that, the box that reads “The key is provided for me automatically” is checked. Uncheck this box. Enter your WPA key in the “Network key” box, and type it again in the “Confirm network key” box. Click OK and then OK again. Now the PC can connect to your network using WPA encryption.

Knowing that you have a bandwidth moocher is one thing, but kicking him off your network is another thing entirely. Sometimes a warning will suffice, but if one of you isn’t using the Windows Messenger service, you won’t even be able to warn him. So, what to do if you can’t get through, or you can get through and the moocher ignores you?

You can kick him off your network using your wireless router’s built-in capabilities. How you do this varies from router to router, but here’s how to do it using the Linksys BEFW11S4. Go to the administrator’s screen by going to http://192.168.1.1. Leave the username blank, type admin for the password, and press Enter. (If you’ve changed the username and password from the default, use those instead.)

Next, click Status, and from the screen that appears, click Local Network. A page will appear with basic information about your router. Click DHCP Client Table, and you’ll see a list of all the devices on the network with their IP addresses and MAC addresses, as shown in Figure 7-20. Check the box next to the intruder and click Delete, and he’ll be kicked off your network.

Figure 7-20. Kicking WiFi bandwidth moochers off your network by deleting them from the IP table

To make sure he can’t get on again, you can tell your wireless router not to allow him onto your network. In my example of a Linksys router, log on to the administrator’s screen and click Security. From the page that appears, click Edit MAC Filter Setting. On the Filtered MAC Address page that appears, you’ll be able to ban devices with specific MAC addresses from getting onto your network. Type in the MAC address in an empty box, and click Apply. From now on the intruder will be barred.

Of course, someone else at some point might try to get on as well. Your best bet to keep out intruders is to use encryption and to limit the number of IP addresses on your network. Also, refer to [Hack #68] for several additional security measures you can take.

The Internet is not the cooperative, friendly place it used to be several years ago, particularly because of the spamming scourge. When spam and scams weren’t much of a problem years ago, it was easy to send mail even when you were outside of your normal ISP’s network—and you’re outside your ISP’s network when you’re at a hotspot rather than at home or an office on a broadband connection, or when you’re dialing directly into your ISP.

ISPs used to allow anyone to use their SMTP servers to send mail. But when spam became a big-time problem, they cracked down on that because it allowed spammers to hide the true source of the origin of their spam. Now, most ISPs won’t allow anyone outside their network to use their SMTP servers to send mail. So, when you’re at a hotspot outside your ISP’s network, you’re treated like any outsider, and you won’t be able to use the normal SMTP server to send mail.

There are several ways around this problem. The easiest is to use the SMTP server used by the hotspot. Find out the server address, configure your email software to use it, and you’re ready to go.

Didn’t know that hotspots have SMTP servers? Join the club. Most hotspot providers don’t publicize that fact. In fact, often, their technical support departments don’t even know they have SMTP servers. I made several calls to T-Mobile asking about it and was told each time the servers don’t exist. In fact, though, they do.

The big national hotspot providers all have SMTP servers, although smaller mom-and-pop shops most likely don’t have them. So, here are the SMTP servers for popular hotspot providers:

If you happen to connect to a hotspot at a hotel, ask whether the hotel has an SMTP server you can use.

How you configure SMTP varies according to the email software you use. If you use Outlook, choose Tools → Email Accounts and then click “View or change existing e-mail accounts.” From the list that appears, choose your email account, and click Change. In the “Outgoing mail server (SMTP)” box, type in the name of the SMTP server you want to use (for example, http://mail.boingo.com), as shown in Figure 7-21. Click Next and then click Finish. Now you’ll be able to send email at a Boingo hotspot.

Figure 7-21. Configuring Outlook to use Boingo’s SMTP server

If you use Outlook Express, choose Tools → Accounts, select the Mail tab, click the Properties button, and then select the Servers tab. In the “Outgoing mail server (SMTP)” box, enter the name of the hotspot’s SMTP server. Click OK, then OK again, and then Close. You’re all set.

What if your hotspot provider doesn’t have an SMTP server? There are still a few solutions for you. One is to pay an SMTP relay service so that you’ll be able to send mail from any hotspot, even if the hotspot provider doesn’t have an SMTP server. Pay the relay service, and then you can use its SMTP server no matter where you are. Configure your email software to use the server, as outlined earlier in this hack, although you should check with the service, in case it has any special setup instructions.

Here are two reputable relay services:

There’s one more solution you can turn to. You can install an SMTP server on your own laptop. Then, when you send mail, you configure your laptop to use that SMTP server to send mail. A simple one to set up and use is 1st SMTP (http://www.emailarms.com/downloads/1st_smtp.html). It’s shareware, so you can try it out for free, but it costs $49 if you continue to use it.

Some metropolitan areas are so full of hotspots that several of them are available from the same location. When I go to Davis Square, located a few blocks from my house in Cambridge, sit at a café, and fire up my laptop, depending on which café I’m sitting at I usually see at least two hot spots, and sometimes three or more.

If you’re near several hotspots and the connections are weak, your connection will stutter and jump; when one connection fades out, XP will automatically connect you to another one, and that one will stutter, and XP will jump to another connection, and so on. The upshot is that you’re never connected to any one of them long enough to maintain a useful Internet connection.

Stuttering is caused by the very thing that allows you to easily connect to hotspots, XP’s Windows Zero Configuration (WZC) applet, which runs automatically on startup. When running, WZC looks for a new network connection every three minutes, and if, at the point it’s looking for a connection, your current connection fades out, it will search for a new one, and then automatically connect to it. The result is stuttering, jumping, and general uselessness.

How to hack it? Temporarily disable WZC after you’ve made a connection; that way, it’ll stay with your one connection, even as it fades out and in. After you’re finished at the hotspot, turn WZC back on so that the next time you want to connect to a hotspot or your home WiFi network, it will do its job.

To temporarily disable WZC, select Start → Run and in the Open box, type services.msc, and press Enter. This runs the Services console. Scroll down until you see the Wireless Zero Configuration entry. Right-click it and choose Stop, as shown in Figure 7-22. That turns the service off; you’ll stop the stuttering and jumping. When you’re done with a hotspot, repeat the steps, except choose Start.

Figure 7-22. Temporarily turning off the WZC service to stop hotspot stuttering

Turning WZC on and off can be a time-consuming chore. So, if you frequently connect to hotspots that stutter, you can speed things up by creating a desktop shortcut that, when double-clicked, will stop WZC, and creating another shortcut that, when double-clicked, will start it back up.

To do this, in Windows Explorer go to C:WindowsSystem32. Drag the Net.exe file to the desktop. Right-click it and select Create Shortcut. Give the shortcut a name by right-clicking it, selecting Rename, and typing in a name, such as Halt WZC. Right-click the shortcut again, choose Properties, and click the Shortcut tab. The target field will read something like this: C:Documents and SettingsAdministratorDesktop et.exe. Replace this with C:WINDOWSsystem32 et.exe, enter a space, type stop wzcsvc, and click OK. Now the contents of the target field should be C:WINDOWSsystem32 et.exe stop wzcsvc.

Repeat these steps to create a shortcut for starting WZC. Name it Start WZC, and type C:WINDOWSsystem32 et.exe start wzcsvc in the target field.

Now, whenever you want to stop WZC, double-click the Halt shortcut. To start WZC back up, double-click the Start WZC shortcut.

My own initiation into Bluetooth was when I needed a new mouse for my laptop. I had avoided buying one of the infrared wireless mice because of the line-of-sight issues, but a Bluetooth mouse seemed like just the ticket. I purchased a Bluetooth dongle that plugs into my laptop’s USB port and a Bluetooth wireless mouse. In addition to the dongle-type adapters, you can also get permanent Bluetooth cards that go into the PCI slot of your desktop computer. The installation procedure is mostly the same.

The Plug-and-Play mechanism in Windows XP works so well that I usually just attach any new piece of hardware without bothering to use the software CD unless I have to. But due to the way that Bluetooth works, it’s best to install the software first so that you have an opportunity to configure Bluetooth prior to using it.

When you install the software, you’ll find the usual assortment of wizard pages asking you where you want to install the software and such. The installer might display a warning about Bluetooth devices and signed drivers. This is a security precaution and a convenience for you. If you click OK, the installer will temporarily disable the signed drivers messages to install the Bluetooth adapter. Otherwise, you would end up with a lot of messages about unsigned drivers.

Once the installer is complete, attach your Bluetooth adapter. If you have a PCI Bluetooth adapter, install the card in an open slot and restart your PC. Windows XP will detect the adapter and associate the drivers with those that you installed earlier. You will probably see several messages show up in the system tray as it installs the drivers for the Bluetooth adapter.

Once Windows XP has finished loading the drivers, you can start configuring your Bluetooth adapter. The My Bluetooth Places icon, shown in Figure 7-23, will open a window that allows you to discover and browse nearby Bluetooth devices. There is also an icon in the system tray for Bluetooth; it’s a blue circle with the runic B on it. The B in the system tray icon changes color depending on the status of the Bluetooth connection—red for when no Bluetooth adapter is connected, white for when an adapter is connected, and green for when a device is communicating with your PC.

Figure 7-23. The My Bluetooth Places desktop icon

Open the My Bluetooth Places window. If you have a Bluetooth device nearby and it is turned on, it might show up on this list. Ignore any devices for the moment while we go through the configuration process. In the upper-left corner of My Bluetooth Places, there is a list of links under the heading Bluetooth Tasks. Click the link labeled Bluetooth Setup Wizard. The choices you are presented with, shown in Figure 7-24, pertain to how you want to use your Bluetooth adapter. For now, choose the last option, the one that begins with “I want to change the name...”.

Figure 7-24. Bluetooth Setup Wizard

If you want to set up service for a particular type of device, such as a mouse or a printer, choose the button labeled “I know the service I want to use...”. If you want to connect to a specific device (in case more than one person is using a Bluetooth device in your proximity), choose the button labeled “I want to find a specific Bluetooth device...” and click the Next button. In this screen, you provide the name of your computer and the type of computer you are using (laptop or desktop). I use a generic name for the computer because this value is broadcast to the world. People who attempt to hack into Bluetooth-connected computers could use this information to their advantage. Click the Finish button to go back to My Bluetooth Places.

If you haven’t already done so, now would be a good time to turn on your Bluetooth device and make sure it is running properly. Click the Bluetooth Setup Wizard link again. This time, when presented with the wizard screen of choices, choose “I know the service I want to use...” and click the Next button. The wizard will present you with a complete list of items that it knows how to communicate with. This is where you will go if you want to add a printer or a headset in the future. To set up the mouse, scroll the list to the bottom, select Human Interface Device, and click the Next button.

The next screen, shown in Figure 7-25, will cause Windows XP to search for all Bluetooth devices in range. If your device does not show up, make sure it is powered on and operating correctly. There might be a Connect or Pair button on the device that you must press to start the communication with the PC. If many devices are in the area, you can use the pop-up box beneath the list to show only certain types of devices. If the device you want to connect is in the list, choose it and click the Next button.

Figure 7-25. Bluetooth Device Selection screen

At this point, the Bluetooth wizard will attempt to connect with the device. If all went well, you should see the confirmation window shown in Figure 7-26. This is your way of knowing the device you are looking for is available and communicating with your computer. Once you click the confirmation button, your mouse and your PC are paired. If you ever see this window and you weren’t expecting it, it could be a sign that someone nearby is attempting to communicate with your computer via the Bluetooth connection.

Figure 7-26. Bluetooth confirmation dialog

If you are planning to add multiple Bluetooth products to your computer, you add them by going to the Bluetooth Setup Wizard and choosing the “I know the service I want to use...” option for each device. Different devices will follow the same instructions as we’ve done with the mouse in this example, although there might be device-specific settings that you will have to configure once the connection is made.

Bluetooth can make your computing experience more convenient by eliminating some of the need for cables. Unfortunately, because the signal is being broadcast on open frequencies, anyone is free to listen in or even participate in the discussion. That’s why it’s necessary for you to take precautions.

The first precaution is to enable only the services you need for your computer. In the Bluetooth Setup Wizard, the choice labeled “I want to configure the Bluetooth services...” allows you to enable and disable different types of Bluetooth communications. Disable any types of communications that you do not plan to use at that moment. Click the Finish button when you have made the changes you need. These services can be easily re-enabled through the Bluetooth Setup Wizard or from the link labeled View My Bluetooth Services.

The next precaution involves locking out other devices. Go to My Bluetooth Places and choose the link labeled “View or modify configuration.” The Bluetooth Configuration dialog box, shown in Figure 7-27, allows you to choose how your Bluetooth connection communicates to the outside world.

Figure 7-27. Bluetooth Configuration screen

Click the tab labeled Accessibility. Remove the check mark from the box labeled “Let other Bluetooth devices discover this computer.” This will prevent unwelcome intrusions by unknown devices. The Discovery tab allows you to configure which devices your connection can discover. This is useful if you are in an office environment with many different types of Bluetooth devices. The Local Services tab lets you configure how different types of devices interact with software services installed on your PC. This will be necessary for synchronizing a PDA, listening to music, or transferring files.

Two of the more publicized Bluetooth security problems are called Bluejacking and Bluesnarfing. Both of these exploits require the attacker to be within communication range of the victim, which is less than 32 feet (10 meters) for most phones and laptops. Bluejacking involves the unsolicited receipt of messages to a Bluetooth device, usually a phone. It’s primarily used as a prank; your phone starts vibrating and you get a message criticizing your hairstyle or the brand of phone you are using. Your attacker will be close by, and chances are good that he is around 15 years old. Bluesnarfing is more dangerous because the attacker is out to retrieve datebook and contact information from your phone. In both cases, if you disable the Bluetooth features of your phone when you aren’t using them, you won’t have these problems.

Bluetooth provides many of the same features WiFi does. Bluetooth has a maximum data transmission rate of somewhere around 100,000 bytes per second, which is much lower than 802.11. Plus, its limited range means all the parties must be in very close proximity. For these reason, it’s not an effective competitor to 802.11 for day-to-day wireless networking.

There are times, however, when an ad hoc wireless network using Bluetooth could be useful. If no network is present and no one has a floppy or flash drive handy, you can use a Bluetooth connection between the computers to share files. Keep in mind that the data rate for Bluetooth is miniscule compared to 802.11, so use it sparingly. For details on how to transfer files between PCs with Bluetooth, see [Hack #74] .

For details on how to pair your PC via Bluetooth with another device such as a cell phone to connect to the Internet, see [Hack #73] .

—Eric Cloninger

Bluetooth also allows you to set up ad hoc networks. In fact, by their very nature, Bluetooth connections are in essence ad hoc networks. So, every time you set up a Bluetooth connection, you’re setting up an ad hoc network. For details, see [Hack 72] and [Hack #73] .

To transfer files between two PCs with Bluetooth, first pair the PCs [Hack #73] . Then, from one PC, right-click the other paired PC and choose Discover Available Services. You’ll see a file transfer icon. Double-click it. Depending on the security settings, you might be prompted to enter a PIN. If so, you’ll use the same PIN on both PCs.

The other PC will now show up in My Bluetooth Places, and now you can navigate through it to transfer files from it to your PC.

You can use an ad hoc network to share a single Internet connection among multiple users. In that case, the user that sets up the ad hoc network configures his PC to allow others to share his Internet connection. Then, when other PCs connect to the ad hoc network, they can get onto the Internet. Of course, to be able to do this, the PC has to have a live Internet connection, such as a broadband cable modem or DSL modem connection.

On the PC that set up the ad hoc network, right-click My Network Places and choose Properties. The Network Connections dialog box appears. Right-click the wireless connection and choose Properties. Click the Advanced tab to bring up the dialog box shown in Figure 7-32.

Figure 7-32. Sharing your ad hoc network’s Internet connection with others

Check the box next to “Allow other network users to connect through this computer’s Internet connection” and click OK. Don’t check the box next to “Allow other network users to control or disable the shared Internet connection,” unless you want to give them that kind of control over the connection. Then click OK again.

If you have servers or network services on your PC that you want to give others access to, such as FTP servers and mail servers, click the Settings button and put checks next to each server or service. Then click OK and OK again.

When you do all this, your PC will function like a DHCP server and hand out private network addresses to the other PCs accessing the Internet. In essence, you’re turning your PC into a wireless router.