"They don't want to risk a potential re-spend."

Marshall 8e6 provides blacklist filtering -- where the filter bans websites against a basic URL list --for about half of US schools. The vendor provided its along with advice on implementation held last year. However, each of the ISPs configured the product independently. NetSweeper, meanshile now sources "considerably" more revenue for the technology overseas than in Australia.

Netsweeper regional managing director, Michael Grace, said the largest ISPs have been "dragging their feet" in regards to adopting optional content filters.

"This hiatus is slowing down the adoption of filtering. The ISPs want either a 'yes' or 'no' from government," Grace said. "I can't help but smile ironically at since I am doing more sales outside of Australia where there isn't the uncertainty of legislation."

Suzie Brady, spokeswoman for communications minister Stephen Conroy, that introduce "wider levels of filtering on a commercial basis".