Expert: Carolyn Meinel - 3/21/2007

Question
QUESTION: I just switched from dialup to DSL.  Please advise whether DSL poses any different security issues.  Thank you for your generous help.
ANSWER: Good question. DSL is usually safer than dialup because, depending upon your DSL provider, your DSL modem probably includes a firewall.

However, some DSL providers don't do a good job of protecting their customers. Most importantly, this firewall might not be secure, it might even allow bad guys to to break into your DSL modem. Once they get into your modem, they could cause all sorts of trouble.

Here's how to make certain that your DSL modem is as safe from attack as possible. Usually you can view and change the settings on your DSL modem by bringing up your browser and typing 192.168.0.1 into the address bar. If this works, you should get a control panel with a menu of things you can change on your modem. Look for something that allows it to reset its password and change it! Next, see if it has a setting to prevent anyone from accessing the control panel from the Internet, and make certain it forbids access except from your home computer.

If 192.168.0.1 didn't bring up your control panel, here's how to find the address. Click Start --> Run and type cmd.exe into the box, then hit enter. At the command prompt type "netstat -an" and you will get something that looks like this:

C:\Documents and Settings\Carolyn Meinel>netstat -an

Active Connections

 Proto  Local Address          Foreign Address        State
 TCP    0.0.0.0:135          0.0.0.0:0          LISTENING
 TCP    0.0.0.0:445          0.0.0.0:0          LISTENING
 TCP    0.0.0.0:1025          0.0.0.0:0          LISTENING
 TCP    0.0.0.0:2804          0.0.0.0:0          LISTENING
 TCP    0.0.0.0:6670          0.0.0.0:0          LISTENING
 TCP    127.0.0.1:1025         127.0.0.1:1222         TIME_WAIT
 TCP    127.0.0.1:1025         127.0.0.1:1229         TIME_WAIT
 TCP    127.0.0.1:1025         127.0.0.1:1233         TIME_WAIT
 TCP    127.0.0.1:1028         0.0.0.0:0          LISTENING
 TCP    127.0.0.1:1135         127.0.0.1:1136         ESTABLISHED
 TCP    127.0.0.1:1136         127.0.0.1:1135         ESTABLISHED
 TCP    127.0.0.1:1137         127.0.0.1:1138         ESTABLISHED
 TCP    127.0.0.1:1138         127.0.0.1:1137         ESTABLISHED
 TCP    192.168.1.1:139      0.0.0.0:0          LISTENING

<snip>

The first number on the left hand side after 127.0.0.1 should be the address of your DSL modem.

Some people (me for example) have a more complicated home network with various routers inside the network. For us geeky types, this trick won't work, but in your case it should work just fine.

---------- FOLLOW-UP ----------

QUESTION: The 192.168.0.1 routine didn't work for me, but the "netstat an" command did.  If I understand your instructions thus far, the address of the modem in your example is 1025 (or 1029 in my case). Now, how do I use the address to access the settings for my modem (in a Windows XP system)?  Thanks for your indulgence.

Answer
I'm sorry, I didn't explain well enough how to access the control panel on your DSL modem. In the example I gave you, the first number below 127.0.0.1 was the address of the modem, in that case 192.168.1.1. When you find that number, just type it into the address bar of your web browser and hit enter. This assumes that your DSL modem has a control panel!

Also, you might be able to look up how to control your modem's firewall (if it has one) at the manufacturer's website. You can do a Google search on what you find on the modem. It would be really nice if your DSL provider offers good tech support to walk you through the process, but normally they hire tech support people who just read from a script and can't answer most questions.

If this doesn't work, could you tell me all that you find on the modem about manufacturer, model etc.? I might be able to look it up for you.