One feature that has been often said as being missing in DoudouLinux is parental controls. This is true, a web browser is shipped within DoudouLinux but no parental control was implemented to prevent children to visit “naughty” pages until recently. Of course this was not desirable for a system targeted at children and even small children. Filtering does not pretend to replace parents with software(!) but this is an additional security, simply because you cannot always be beside your children on the computer (and he doesn't want you to surely!).

Well, let's talk about technique now… There are different components in parental controls. Here we only focussed on web filtering. Other components, such as authorized hours of use, will be evaluated later. For web filtering we opted for the famous DansGuardian web content filtering solution. This tool provides two ways of avoiding naughty sites: a classical black list and a less classical real-time content filtering. The second is really an interesting feature: it can block a Google search which would otherwise give “naughty” results. The following screen capture shows a blocked Google search for the word “sex”. Yes this would give mainly naughty results…

DansGuardian error page (French)

However recent tests showed that DansGuardian is not perfect yet - so do not leave your children all day long on the Internet ;). We think that this is due to localization of black lists and keyword lists. Our translation team will then have to do some work to show if localization is really the source of malfunctioning or not.

Concerning the mechanics, a French article provides very good information on how to make DansGuardian run along with Squid, some proxy software. Using both tools and some firewalling rules in IPtables, we get a system in which web page requests cannot avoid DansGuardian[1]. However we had to do some more tuning to ensure that both Squid and DansGuardian are always started after network is actually setup. Without taking care, web access would not work at all whenever the network cable is plugged after DoudouLinux is fully working.

Notes

[1] except if a website is not using the standard port 80, but this never happens…