ISPs Telstra and Optus will use the results of filter trials conducted last year to inform engineers on how to satisfy a commitment to voluntarily block child abuse content.
The two ISPs joined iPrimus last week in committing to block a list of child abuse URLs to be supplied by the Australian Communications and Media Authority (ACMA).
An Optus spokesman said that "any [technical] information we have would be from the trial we conducted last year."
A Telstra spokesman told iTnews that its internal trial of filter technology last year showed "what's possible".
"We're still working through aspects of the implementation," the spokesman said.
"We're confident that a viable solution will be implemented in a timely fashion based on the findings of our earlier trial, as well as the preliminary work our technical team has done to date."
An iPrimus spokesman could not be reached for comment.
Lack of technical detail in last week's announcement was noted by competing ISPs.
"None of them [Telstra, Optus or iPrimus] will have the technical capability before next year," Internode network engineer and filter critic Mark Newtown tweeted.
"[It's] network engineering by press release."
Optus and iPrimus were participants in the official trial of filtering technologies conducted by Enex Testlab on behalf of the Government. Enex handed down the results in October last year.
Telstra conducted its own private tests in the BigPond pre-production labs. However, it did not run tests in a production environment and did not involve real customers.
The official trial and the Telstra test reported "100 percent accuracy" blocking URLs on the ACMA blacklist and a private test list respectively.
The trials supposedly established the technical feasibility of content blocking, but neither telco has been able to provide comment on how long it would take to roll out these capabilities across their networks.
Telstra and Optus spokespeople declined to comment on when the voluntary filters might be ready.
A voluntary code being developed by the Internet Industry Association (IIA) on the back of Telstra, Optus and iPrimus' commitment was slated to precede the technical implementation.
"We are yet to develop the industry code and therefore a lot of the detail is still to be determined," an Optus spokesman said.
The telcos also declined to disclose how much complying with the voluntary blocking commitment might cost them to implement, nor whether or not the Government had committed funds to reimburse their costs in exchange for participation.
"We're not in a position to answer specific questions at this stage," the Telstra spokesman said.