The Australian Securities and Investments Commission (ASIC) has revealed it has used section 313 of the Telecommunications Act 10 times to block websites, also accidentally blocking 250,000 sites.
ASIC told a Senate Estimates hearing on Tuesday that the recent blocking of Melbourne Free University was the first time it was aware that innocent websites had been blocked.
The government agency said it has now reviewed its previous use of section 313 requests to block websites and found around 250,000 websites were blocked in March this year.
The mass blocking of the websites occurred when ASIC blocked an IP address, with the other websites also hosted on the IP address.
It said around 99.6 per cent of the sites contained no "substantive content".
"In this instance we believe that less than 1000 active sites (less than 0.4 per cent) may have been temporarily affected," an ASIC representative said.
It said none of the sites were from an .au domain.
On the eight other occasions that ASIC used section 313, it said only targeted sites were affected or a "small number of other sites" were affected.
ASIC said it is now working with the Australian Federal Police, telco carriers and other law enforcement agencies to determine how it can "disrupt websites" without inadvertently blocking innocent sites.
"In the case of ASIC, we want to be as public as possible because of the nature of what we're trying to do with this with targeting websites. We'd like the public to know about that so we would like to report on our use of the power," an ASIC rep said.
Under questioning from Greens Senator Scott Ludlam, ASIC said there was no correlation between the AFP's use of section 313 and ASIC's recent use of the legislation.
"Senator, I'm not aware that there was any sort of discussion by one agency about its use in relation to one area ... and the suggestion that we use it in relation to illegal activities - fraudulent websites," an ASIC rep said.
An ASIC rep said telco carriers are alerted about section 313 requests via a fax which is primarily only sent to large ISPs.
"We send it to the largest ones and as I understand it ... some of the carriers actually control the pipelines, as it's been described to me, from Australia to the international overseas providers. By serving on those particular carriers we get to the majority."
Section 313 of the Act requires that a carrier do its "best to prevent telecommunications networks and facilities from being used in, or in relation to, the commission of offences against the laws of the Commonwealth or of the states and territories".
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