IP address assigned by DSL modem - security issue

By fberton520 ·
I used to have an ensecured wireless system which means my signal could be picked up by anybody in my neighborhood. I also know that my Yahoo DSL modem assigns a private IP address to my computer which will ping to my Yahoo account. I have a two-part question:

1) Will my DSL modem assign an IP address to any other computer that uses my wireless system signal?

2) Will that modem-assigned IP address ping back to my Yahoo account.

The reason I ask is because someone had/has been using my wireless signal for some questionable activities and the discovered IP address has pinged back to my account. I no longer have a wireless system to protect my security.

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Some explination

by Kjell_Andorsen In reply to IP address assigned by DS ...

OK, I don't know the extent of your technical background, so I might be oversimplifying this a bit, if so I apologize.

Your DSL modem is assigned what is called a Public IP address. This IP address is unique in the sense that no other device on the whole internet can have the same address.

Your Wireless router most likely has what is called a NAT function, NAT stands for Network address translation. Basically what it does is act as a gateway between a private network and the public internet. The Wireless router will give out IP addresses to any system that connects to it. These IP addresses are a special class of addresses called private addresses. The private addresses are not unique, in fact there are thousands of networks the world over that use this same range of private addresses for their networks.

The wireless router NAT function basically translates the private addresses to the unique public address assigned by your ISP. This means that any computer on your private home network will appear to have the same public IP address.

So in essence, yes. If someone is using your wireless network to access the internet, they will appear to have the same public IP address as you.

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thank you very much

by fberton520 In reply to Some explination

Your reply was quite helpful.

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Lock It Down

by rkuhn In reply to IP address assigned by DS ...

A few suggestions so you can continue to use your wireless connection but keep others out.

First, become quite familar with your DSL modem/router...find the manual or website.

1) Use MAC address filtering
2) Limit the number of DHCP addresses to the number of PC's you have
3) Use either WPA or WPA2 encryption
4) Change the default password on the router
5) Disable SSID broadcasting
6) If your wireless network is small, you could reduce the signal strength to only that that is necessary to reach your PC's and get a good signal and speed but no more/no less
7) Make sure you have the latest, greatest firmware installed on the modem/router
Go to and run a Shields Up test

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