Internet filters can reduce the risk of your children coming across across internet content that you don't wish them to come in contact with however they are and can never be the total answer to concerns over internet safety.

Australian families can download or order filters from the Internet Industry Association site

However Filters

"...........do not offer total protection and work most effectively in association with a range of strategies to stay safe online. Internet content filters will not check for computer viruses or provide a firewall that keeps out unwanted viruses or programs."

Be aware that you can quite easily "get around"or circumvent homebased internet filters through the use of proxies. A simple search on Google will locate a range of advice and links on how to get around internet filters like Squiddoo.