German cryptographer Karsten Nohl is presenting a seminar on his findings vulnerabilities discovered in the GSM SIM card platform at Blackhat 2013 (http://www.blackhat.com/us-13/briefings.html#Nohl
Forbes has covered this news here with some explanation of what the hack is about and how it affects mobile phone users here – http://www.forbes.com/sites/parmyolson/2013/07/21/sim-cards-have-finally-been-hacked-and-the-flaw-could-affect-millions-of-phones/
It appears that the vulnerability generally affects GSM systems using the 64-bit encryption technology (http://www.nowpublic.com/tech-biz/gsm-encryption-cracked-karsten-nohl-posts-phone-hack-torrent-2547037.html).
What does this mean for Australian users? None of the carriers has put out a statement on this. However, carriers like Telstra have been using the newer 128-bit encryption technology for a number of years already. Other providers may have also followed suit. At this stage, we can only sit tight and hope carriers will address this issue quickly. In the meantime, monitor your phone usage closely and report any suspicious activity to your phone carrier quickly.