How to use wireless router while still ensuring privacy

Q: We have a wireless router connected to the cable modem for my PC and laptop. One of my friends was outside of the house about 50 to 70 feet away from my router with his laptop and to my surprise he got connected online through my router. Is there a way I can make my router deny access to any PC or laptop? I don't want any strangers passing by my house or neighbors getting access online through my router.

— Ryan Martinez

A: Can't say as I blame you.

Yes, there are things you can do to prevent others from using your wireless-access point to connect to the Internet. Fact is, if they can access your wireless-access point, sophisticated hackers may also be able to access your internal network and the data on your computers.

The first thing to do is to make sure that your wireless access point isn't advertising itself. Most access points by default send out their name so that wireless devices can see the access point is available and connect to it. If you disable the broadcast "station identifier," any user will have to know the name in order to connect to it (sophisticated hackers can get around this tactic, however). The exact steps required to disable the broadcast station identifier depend upon your specific wireless access point.

Next, change the name of the station identifier. Access points come with default names so that you can connect to them. Hackers know these default identifiers.

You can also set up the wireless access point to require encryption by all clients. That way, for a client to connect, it will need to have the correct encryption key. There are several types of encryption with varying degrees of security. The most simple types can be "cracked" relatively easily by hackers, so you'd need to change the keys frequently. Most access points currently support WEP, or Wired Equivalent Privacy, but this protocol is not particularly secure. WAP, or Wireless Application Protocol, is more flexible and secure, but it is not supported by all devices, particularly clients.

Finally, some wireless-access points allow you to specify that only devices with a specific machine address can connect. Again, this isn't foolproof, since hackers can spoof machine addresses. But this does present at least another hurdle a hacker must get over.

The bottom line is this: The more concerned you are about security, the more steps you'll want to take to block hackers. Unfortunately, each measure you take involves learning, time and, in some cases, money.

Q: I have a number of drives on my Windows XP PC and all defrag normally. However, my C: drive doesn't. I receive a message that says "CHKDSK is scheduled to run" when I try to run the defragmentation utility. How can I satisfy the CHKDSK /f command?

— Carl Murray, Seattle

A: The screenshots that you sent with your question indicate that CHKDSK is not able to complete because the volume — the file system on drive C: — is being used by another process. (For readers who may not know, the /f switch used with the CHKDSK command causes the utility to repair any problems it finds.) Likewise, that would prevent the defragmentation utility from working.

So what process or program might be using the drive? That's a tougher question to answer. In fact, it could be anything from an antivirus program to a virus. Or it could even be a corrupt file or sector on the drive tripping things up.

I'd recommend you boot from a floppy disk drive or a CD drive using a system disk, then try running CHKDSK /f on the C drive. That will prevent other processes or applications from loading that might be causing the problem. If the problem is a physical one with the drive, however, you may need to try a low-level reformat or, possibly, a new hard drive.

Questions for Patrick Marshall may be sent by e-mail to pmarshall@seattletimes.com or pgmarshall@pgmarshall.net, or by mail at Q&A/Technology, The Seattle Times, P.O. Box 70, Seattle, WA 98111. More columns at www.seattletimes.com/columnists.