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Beginners Guides: Firewall Setup and Configuration
Beginners Guides: Firewall Setup and Configuration - PCSTATS
Firewalls are a necessity, but configuring them so that every internet-based program still works is often troublesome. With this guide, you can have your Firewall, and MSN File Transfers too.
Filed under: Beginners Guides Published:  Author: 
External Mfg. Website: PCSTATS Jul 31 2007   M. Dowler  
Home > Reviews > Beginners Guides > PCSTATS

Strengthening Home router firewalls

This is a tricky subject, as there are a wide variety of possible settings, and not every home router will have certain options. What we will do is give you a list of potential settings and what they can do for your firewall's security. Compare these to your devices' documentation and configuration to ensure that you are fully secured.

Block ICMP traffic, or 'stealth' mode: Not every home router comes set to reject ICMP traffic by default. ICMP is the protocol used most commonly by the PING program, which queries a given IP address and reports back if a computer answers. This program forms the basis for the myriad of 'scanner' programs freely available on the Internet. These scan a range of IP addresses for responding computers. The systems that answer back to the ICMP request are then targeted by the scanner for further, more intrusive measures to discover security weaknesses. If your firewall blocks ICMP traffic, your system is effectively invisible to casual Internet snoopers.

Stateful packet inspection: Certain firewall products may feature stateful packet inspection as an option. This firewall method takes a deeper look at each data packet received, instead of just approving or dropping them based on the set rules of the firewall (allow x data from y computer on z port). A stateful firewall will compare a data packet to others received previously, and will also examine the full contents of the data. This enables them to prevent attacks that traditional firewalls would not catch, such as a DoS (Denial of Service) attack made up of massive amounts of identical data packets intended to overwhelm the target system.

Disable remote administration: Most home routers have a feature whereby the configuration screens can be accessed from the Internet with a username and password. Obviously, disabling this feature increases the security of your setup, especially since the devices ship with a default password which many users forget to change.

Attack detection: Many home routers have a feature where they specifically identify and log certain common types of attack, like denial of service attacks or certain well-known exploits.

Disable file and printer sharing: This one should be on by default with most home routers, if it exists at all, but check just to make sure. When on, file and printer sharing allows remote users to access shared files and devices on your system.

Configuring your firewall for common applications

Now that your firewall is set up correctly and configured for maximum security, it's time to make sure that the Internet applications you commonly use play nicely with your newly secured and firewalled internet connection.

Firewalls can play havoc with certain programs that need unhindered access to several ports to carry out their duties. One good example is the file transfer feature found in popular instant messaging programs like MSN Messenger and ICQ. Peer-to-peer file sharing programs like Kazaa and Shareza can also be affected, as can Internet-connected multiplayer games.

Fortunately, allowing access for these programs is generally simple, especially if you are using a software firewall like the XP firewall or Zonealarm. Hardware devices can be a little harder to work with, but it's still generally easy to get around.

The most difficult step in this procedure is actually discovering which ports need to be opened for certain programs. Generally this information can be obtained fairly easily by visiting the website of your software's manufacturer, but there are alternative methods. The easiest of these is to download a tiny freeware program called TCPview by Sysinternals. This excellent little utility gives you a graphical, realtime view of all active connections on your system. If a program on your system connects to the Internet, TCPview will tell you and show the port it's using.

Let's look at how to use the program.


Upon running TCPview, you will be greeted with a screen full of information. Very overwhelming.

This is because by default, the software lists all listening ports as well as those that currently have connections. To cut the view down to something more manageable, open the 'options' menu and uncheck the 'show unconnected endpoints' option.

Much better.

Assuming you have your browser open (and if you don't, how are you reading this...?) you should see one or more lines with the identity of your browser on the far left. Each of these lines represents an active connection between your computer and a remote host.

The third column 'local address' shows the name of your computer and the port number that is being used for that particular connection. So 'mainbox:4356' indicates that that particular connection is using port #4356. Experiment by opening up new browser windows or chatting on an instant messaging program.

Using this utility, you can determine what ports any software needs by running the software and noting down the connections that it makes. Of course, you will need to deactivate your firewall during this process, so that it does not prevent the connections from being made. For the WindowsXP and Zonealarm firewalls, you can easily deactivate or close them, but for home router firewalls, you will need to either disable the firewall within the device's configuration (if the option exists) or connect your PC directly to your DSL or cable modem while you are testing.

Let's take a look at configuring our three firewall examples for a variety of common applications. Even if your chosen Internet software is not represented here, you should be able to figure out the necessary process from these instructions.

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Contents of Article: PCSTATS
 Pg 1.  Beginners Guides: Firewall Setup and Configuration
 Pg 2.  Activating the Windows XP firewall
 Pg 3.  Zone Lab: Zonealarm
 Pg 4.  Home Internet sharing device firewalls
 Pg 5.  Strengthening the pre-Service Pack 2 XP Firewall
 Pg 6.  — Strengthening Home router firewalls
 Pg 7.  Allowing applications through a Windows XP firewall
 Pg 8.  Configuring Exceptions with the SP2 XP Firewall
 Pg 9.  Hosting with the Windows XP Firewall
 Pg 10.  Virtual Server Firewall Configuration

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