Australia's anti-corruption investigator for law enforcement agencies has argued in favour of mandatory telco data retention on the basis that matching an IP address could have saved a recent case that went awry.
The Australian Commission for Law Enforcement Integrity (ACLEI) said in a submission to a Senate inquiry on telecommunications interception that the refusal of ISPs to retain user activity data had shut down a crucial avenue in a recent corruption investigation.
"It appeared that sensitive information about a law enforcement agency may have been unlawfully disclosed to a third party by use of an anonymous website contact form," ACLEI told the inquiry (pdf).
"[We were] able to identify the IP address of the computer from which the alleged unlawful disclosure had been made, but when [we] sought to match the IP address to a particular internet user, the relevant internet service provider advised that—in accordance with usual business practices—the information had been destroyed when it was no longer necessary.
"There were no other means available to ACLEI to match the IP address to a person."
ACLEI said that if the ISP had been obliged to keep data "for more than a few months", the situation might have been different.
The notion that an IP address can be used to positively identify a person is fiercely disputed.
A landmark piracy case between the film industry and ISP iiNet also served to disprove any linkage between an IP address and a specific internet user — in that case, to work out who might have downloaded pirated material from a particular device.
"There is no way to directly link an IP address to a specific person for further investigation," iiNet said in a whitepaper (pdf).
"Assumptions can be made, but if a proprietor was running a coffee shop or a small business and providing wireless internet access for customers when their IP address came up on somebody’s list, they would be at a loss to point to a suspect."