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Is My IP Address Public or Private?

Every computer on a network has to have an address that is unique on the network.  These are called Internet Protocol Addresses or IP addresses.  There are two kinds of IP addresses, public IP and private IP addresses.  Your ISP generally assigns a public IP address to the edge device, the DSL modem or cable modem.  Many ISPs also assign one public IP address to the first device attached to the modem.  In many cases this is your computer.  Devices with assigned public IP addresses are visible from the Internet.  This means hackers with the right skills and software tools can find your computer, explore it for weaknesses, and finding any, gain access to your computer.

You can discover what your IP address is by performing the following:

  • Click on Start, Run.  When the Run dialog box opens, type cmd in the window, and click OK.

  • This will open a DOS-like command window.  At the flashing cursor, type ipconfig.  Press Enter.

  • Your Windows networking configuration will be displayed.  If your IP address begins with the numbers 192, 172, or 10, your computer is already protected behind a firewall or gateway router that is running NAT, and is invisible to hackers from the Internet.

If your IP address starts with anything else, you are running on a public IP address, and your computer is under a continual state of attack from port scanners and other hacker exploits.  You are at risk for infection; you may be infected already.  You need to consider getting a hardware firewall device.

Hardware Firewall

A hardware firewall is a device that sits between your Internet connection and your computer.  They will provide Network Address Translation (NAT) at a minimum.  Many of these come with basic stateful packet inspection firewall and virtual private networking (VPN) capabilities.  Most newer cable or DSL modems have this capability, and some will provide a wireless network as well.  If yours does not, call your service provider for an upgrade.  A good alternative can be found in cable and DSL gateway routers and wireless access points made by Linksys, D-Link, or Netgear.  They can be purchased for $50 to $100 dollars.   Usually they have a 4 port switch, which gives you the ability to connect several computers to your internet connect.  A wireless access point will allow you to connect even more devices, without having to run network cables. 

NAT works by exchanging the public IP address that your ISP provides, for a private IP address that is not “routable” or visible to other machines on the internet.  Crackers can only get to your gateway router, and there is nothing there for them to do, so they move on to easier targets.

Port blocking works by closing ports that are not needed by installed applications, and preventing crackers with port scanners from finding an open access point into your network.

Stateful packet inspection works by looking into each data packet as it arrives.  The firewall compares the source and destination addresses and ports for known malicious activity, and ensures that incoming packets are the result of earlier outbound requests from you.

 

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