The third filtering option is the hardware filter. Every computer or device in the home, which is connected to the Internet, connects through some sort of residential Internet gateway (commonly referred to as a router). Typically, these gateways only serve one purpose: sharing the Internet access across all of the Internet capable devices in the home. In this third filtering option, the typical gateway is replaced with a gateway which includes filtering. Like the software filter, the hardware filter can provide a number of different features ranging from basic filtering to user access control and more. Since the hardware filter becomes the gateway for the home network, any device attempting to access the network through the gateway is filtered subject to the rules of that gateway. Therefore, the hardware filter has the significant advantage of forcing filtering and rules on all devices, regardless of the type of device or operating system. Second, the only way a gateway filter can be defeated is by physically removing the filter and replacing it with another gateway. This can be prevented very simply by placing the gateway and your ISP’s modem in a locking cabinet.

As with all products, there are pros and cons to each. In this case, the use of a hardware firewall requires an investment in the hardware and either a continuing investment in the service or a moderate level of technical skill to maintain the device. In the past, hardware filters have had a bad reputation of slightly degrading the performance of an Internet connection. As the hardware has advanced, this has become less of a problem.
 

The first filtering method is DNS blocking. The acronym DNS stands for “Domain Name Service.” Essentially, every device on the Internet has an address. However, those addresses are not necessarily easy to remember by humans. An Internet address is a set of four numbers separated by periods where each individual number is a number between 1 and 255. So, an Internet address might look something like this: 174.121.19.22. Actually, at the time this article was published, that was the address of the server Teens-4-Christ was hosted on. So, which is easier to remember: Teens-4-Christ.org or 174.121.19.22? The DNS is a database of every domain name (Teens-4-Christ.org) which maps that name to the proper server’s address (174.121.19.22). It is like saying I am going to the White House as opposed to saying I am going to 1600 Pennsylvania Ave, Washington, DC. The term “White House” becomes a friendly name for the physical address. Likewise, “Teens-4-Christ.org” is a friendly name for the physical address “174.121.19.22.”

So, when you type a human readable name such as “www.Teens-4-Christ.org” into your web browser, how does your computer know where to find that address? Your computer must ask a DNS server. In most cases, your Internet service provider, or ISP, provides you with access to their DNS Server. However, you can change that. So, suppose your computer asks for, hypothetically, “somepornsite.com” your ISP will dutifully return the address of that site. However, if you were using a DNS server which knew you didn’t want to go to porn sites. Instead of returning the correct address of the unwanted site, it would send you an address which may point to nothing or an address which may point to an error page. Your computer doesn’t know the difference. It will receive an address and try to load whatever content is at that address.

Using DNS blocking requires no software to be installed on the device and it does not require any external hardware. It does, however, require some technical knowledge to implement. It can also be easily defeated by a modestly savvy user. One example of a DNS filtering service is OPENDNS (www.opendns.org). DNS filtering has the advantage of working on any device.