Australian telecom firm Optus’ account website and pre-paid mobile SIM activation system were successfully breached by an unknown user named Vladmir or Sarah Some customers claimed that they can view the customer information of someone else contacts details and personal data the moment they try to activate their SIM card. This cross access can only happen if something went wrong with the account database that Optus is using in order to authenticate users with their SIMs.”]
Source: https://hackercombat.com/bad-valentines-for-optus-as-sim-activation-system-got-hacked/