A federal government move to stamp-out illegal file sharing via the national Internet content filtering scheme will be impossible, experts say, without blanket ban on peer-to-peer traffic.

Communications minister Stephen Conroy issued the furtive announcement last month in a government blog that ISPs may be required to block illegal file sharing in peer-to-peer networks -- used by the likes of LimeWire, Kazaa and BitTorrent clients.

"Technology that filters peer-to-peer and BitTorrent traffic does exist and it is anticipated that the effectiveness of this will be tested in the live pilot trial," Conroy wrote in the blog.

The national clean feed Internet scheme, part of the government's $128 million Plan for Cyber Safety, will impose national content filtering for all Internet connections and will block Web pages detailed in two blacklists operated by the Australian Communications and Media Authority (ACMA).

Penetration testing firm Assurance.com.au director Neal Wise said blocking illegal content over peer-to-peer traffic is too resource-intensive and detrimental to legitimate traffic to be feasible.

"It is one thing to use a proxy server to ban a list of Web sites, but other application protocols are a whole other thing -- many peer-to-peer [networks] are particularly cunning and get around firewalls and packet filters," Wise said.

"[Both filters] can be easily defeated. The Internet routes around damage and people will get around it if it becomes mandatory... the hackers always win.

"In all likelihood the practical way this will be implemented is by blocking or throttling all peer-to-peer, rather than doing it selectively."

He said enforcement will be difficult because current technology cannot effectively filter the huge reams of data travelling over the networks and ISPs are unwilling police users.

The announcement follows criticism that Web filtering will not block the large amount of illegal material distributed across peer-to-peer networks.

Pure Hacking senior security consultant Chris Gatford said ISPs lack the resources to block only illegal material which requires potentially billions of shared files to be verified.

"It will be an extremely arduous task and I don't believe there is technology capable of filtering the huge amount of data," Gatford said.