
Over-blocking refers to the censorship of harmless content.
Medium-to-large Australian ISPs routinely carry in excess of 100,000 HTTP requests per second during peak times, SAGE-AU said in a statement.
Under ideal conditions with the best-of-breed filter in place, those ISPs would be incorrectly blocking over 3,000 HTTP requests every second.
“It is difficult to believe that the helpdesk requests required to manually unblock that volume of errors will not come at a significant cost, or that that cost won't increase Australian Internet access prices,” the statement said.
Don Gingrich, SAGE-AU member and lecturer in System Administration at RMIT University, added, "From past experience in looking at how this has played out in other regions, there seems to be a near certainty that legitimate and useful educational sites will be inadvertently blocked as a part of any effort of this sort.
“A 'little bit censored' seems a lot to me like a 'little bit pregnant'," said Gingrich.
The Guild also claims the filtering regime will undo any benefits from a future Fibre to the Node (FTTN) network, due to the delays and processing required by the content filters that were tested.
Preliminary results from the ACMA study showed that five of the six filters tested degraded Internet throughput speeds by at least 22 percent.