BBC News, Sydney
Critics of the filtering plan fear it will slow net speeds
Is the Rudd government about to erect a Great Firewall of Australia - introducing a form of internet censorship that will infringe upon the freedom of computer users to browse the worldwide web?
That is the concern of online civil liberties groups, as the Rudd government prepares plans for a field trial of internet service provider (ISP) filtering products, with a view to introducing them nationally.
ISP filtering is the blocking of certain sites which the government deems illegal or inappropriate, and is the central plank of the Rudd government's "Plan for Cyber-Safety".
The official watchdog, the Australian Communications and Media Authority (ACMA) has been conducting laboratory tests of six filtering products, and the government plans a live trial soon.
"Although the internet has opened up a world of possibilities and benefits for Australian children," noted communications minister Stephen Conroy when he announced his intention to police the internet earlier in the year, "it has also exposed them to continually emerging and evolving dangers that did not previously exist."
The aim, he said, was to create a safer online environment for Australian children.
But the government has been very tight-lipped about its plans. That information vacuum has been filled on the blogosphere by concerned internet users.
Much of the angry online chatter and speculation has centred on whether internet users will be able to opt-out of the filtered "clean feed".
China is known for operating tight control over net access
Senator Conroy has stated that Australians would be given the opportunity to opt-out, and that the scheme would therefore not be mandatory.
But a network engineer from one of Australia's leading net suppliers, Internode, has challenged that assertion, arguing that there would be two black-lists. One would contain unsuitable and harmful material for children; the other would include inappropriate material for adults.
Mark Newton of Internode wrote in an online forum: 'The much-touted 'opt-out' would merely involve switching from blacklist number 1 to blacklist number 2….Regardless of your personal preference, your traffic will pass through the censorship box.'
Senator Conroy has since indicated that there would be a two-tier system: a mandatory one that would block all "illegal material" and an optional tier that would block material deemed unsuitable for children, such as pornography.
The opponents of ISP filtering have practical as well as philosophical concerns.
Firstly, there are worries about online censorship.
The website, "No Internet Censorship for Australia" asks: "Do we really want the Government of the day deciding what Australian adults can and can't see? Do we want Australia to join a censorship club in which Burma, China and North Korea are the founding members?"
Then there is the problem of what online free speech advocates call "censorship creep".
It is easy to mix up a site criticising child sex tourism and one promoting child sex tourism.
Dale Clapperton, EFA
"Even if the filtering system only targets child pornography to begin with, we have no confidence it will stay that way," says Dale Clapperton of the online civil liberties organisation, Electronic Frontiers Australia (EFA). "It will be subject to creep. Everyone with any lobbying clout will be after the government to ban their pet peeve websites.'
These fears are exacerbated by the political balance of power in Canberra.
Though the governing Labor Party has a comfortable majority in the House of Representatives, it has to rely in the upper house, the Senate, on the Greens, an independent from South Australia and the socially conservative Family First Party.
Family First's sole parliamentarian, Senator Steve Fielding, recently single-handedly blocked the government's initial proposals for a luxury car tax. Freedom of online speech advocates fear he could use his influence to push for even greater controls on the internet.
There is also question of what is inappropriate, and who gets to decide. The Greens Senator Scott Ludlam contends: "The black list ... can become very grey depending on how expansive the list becomes - euthanasia material, politically related material, material about anorexia. There is a lot of distasteful stuff on the internet."
There are technical issues, as well, such as the impact of filtering on the speed of the web, which in Australia is already slow.
The technical term is network degradation. After its recent trials, ACMA reported significant improvements on earlier studies. The network degradation on one product was less than 2%, although two products were in excess of 75%.
Censorship creep may afflict the net filtering system say critics
Filtering systems also have a tendency to "overblock", restricting access to legal material.
They look at words, the ratio of images to text and the preponderance of skin colour. They assess content but not necessarily the context in which it appears.
"It is easy to mix up a site criticising child sex tourism and one promoting child sex tourism," says Mr Clapperton of the EFA.
Finally, there is the question of whether the filters will be effective. In the ACMA trials, the filters ranged from an 88% to 97% hit rate.
Even the most successfully restrictive system was by no means water-tight.
Computer experts also say that the filters will not impact peer-to-peer (P2P) file sharing networks, which account for an estimated two-thirds of internet traffic.
"Any determined user - including children - could bypass the filter quickly using an anonymizer service," says the No Internet Censorship for Australia site.Many in the online community fear that Australian government is about to degrade the internet with a filtering system that will not offer any effective protections - that if a way can be found to erect the Great Firewall of Australia, it will be easily and quickly breached.