For parents, one way to restrict access is to use the free service OpenDNS. Simply go to OpenDNS.com and sign up. Download and install the dynamicIP updater client and install to your PC. This updater gives them your IP and allows them to filter your requests as you prefer.
On the settings page, set your filter preferences:
Then configure your router DNS servers to point to those provided by OpenDNS: 22.214.171.124 and 126.96.36.199. When a PC on your network reboots and gets an IP address from your router, it will also assign the OpenDNS servers to the PC.
And your done! You can block specific web sites or types of websites or allow only a few websites. Of course, the child can bypass this by manually configuring their PC to use a different DNS server, but depending on their age and level of expertise, they wouldn’t be doing that. If they get to that point, it may be time to talk to your kids. If that doesn’t work, you may need to use a firewall between your cable modem and router 🙂 .