Setting Up Parental Controls in Ubuntu - page 2
Controlling Computer Usage by Users
When creating accounts for the youngsters, make sure you don't give them administrative privileges. Otherwise they could change settings and mess up the whole system. To create or edit accounts, from the Ubuntu menu click System, Administration, and Users and Groups. When adding an account, you can select Unprivileged for the Profile type. When editing an existing account, you can modify the settings on the User Privileges tab (see Figure 3) of the account's Properties dialog box.
Filtering Internet Content
You have several options when it comes to filtering what sites users can visit. You can either install a software solution on each computer or use a hardware approach where a network router would provide the filtering abilities. For a software solution, you can look into using DansGuardian and Tinyproxy. You might even want to look into Ubuntu Christian Edition, which has filtering and other educational applications preinstalled. However, a hardware approach, such as by using the OpenDNS service on your router, can provide filtering for the entire network. This would eliminate the need to install and maintain a filter on each computer. Some router manufactures also provide built-in filtering features or separate hardware appliances, such as the service from D-Link.
Locking Down Your Ports
Even though you filter the Internet content, you may want to block all but the required ports to the Internet; port 80 for Web browsing, port 53 for DNS service, and port 443 for secured pages. This helps to prevent users from using applications or services that they shouldn't be using. You can block access at the router so you don't have to configure each computer, which would also require you to whitelist or authorize the required ports for local network traffic (DHCP, sharing, etc).