According to the Linux President Joshua Hesketh the breach occurred on the 22nd March, as a large number of error reporting emails were sent by the Conference Management (Zookeepr) hostingserver. This server hosted the conference systems for linux.conf.au 2013, 2014 and 2015, and for PyCon Australia 2013 and 2014.
Although this breach has not deleted the information of these registered people from the Linux servers but because their passwords has been leaked Linux suggested them to change their passwords especially if they are using the same on their other accounts.
Linux Australia identified the breach after 48 hours after the Linux admins noted that Zookeeper (Conference Management Software) started sending large number of errors in reporting emails. After that they discovered that their server was under attack from 22nd march.
Linux Australia released a statement that ” Linux Australia do not believe this was a targeted attack against the Zookeepr conference management system, nor an attempt to harvest details from the system, we are taking the necessary precautions to review, remediate and minimize the risk of exposure to attacks similar to this.”