A European Commission study has found that parental control programs function poorly when filtering Web 2.0 content such as social networking sites or blogs.
In addition, it says, only a few products on the market can filter web content accessed via mobile phones or game consoles - at a time when one child out of four in Europe goes online in this way.
The study analyzed 26 parental control tools for PCs, three for games consoles and two for mobile phones. It found that existing software is pretty good at filtering adult online content.
The tools were analysed with settings for two age groups: 10 year olds and younger and 11+ year olds in English, French, German, Italian, Polish and Spanish. They were tested according to functionality - OS compatibility, the ability to filter content according to keywords, topics and URLs and blocking ability for different types of content.
The study also examined whether the tool could be easily disabled or by-passed by tech-savvy youngsters and whether both beginner and advanced users could easily install the tool on their computer.
But, it says, there's still at least a 20 percent chance that sites with unsuitable material for children and especially those encouraging youngsters to self harm - sites promoting anorexia, suicide or self-mutilation - could pass through their filters.
At the same time, other sites that include content specifically for children are blocked.
Only a few tools, says the report, are able to filter web 2.0 content, block instant messaging or chat protocols or filter contact lists.
In any case, another EU-funded report finds, parents aren't implementing controls often enough. A separate survey by EUKidsOnline found that only about a quarter of parents block or filter websites or track the sites children are visiting.