Perth internet provider iiNet is investigating a possible security breach after details were posted on social media about the sale of the database of a major internet service provider.

Cyber War News posted an image on Twitter yesterday detailing claims of the sale or trade of an extensive amount of westnet.com.au’s database, including passwords. Westnet was acquired in May 2008 by iiNet.

The person offering to sell the details is known only by their two Jabber instant messaging contact addresses: rain@dlab .im and mufasa@tigase.im.

“I am selling the db (database) of a major ISP in Australia,” the person wrote. “Those interested can contact me via Jabber.”

The data could potentially be used to reveal personal details such as phone numbers, addresses and credit card details.

iiNet chief information officer Matthew Toohey said last night the company was investigating.