Optus chief executive Kelly Bayer Rosmarin said the cyber attack was caused by savvy hackers who gained access to around 9.8 million accounts. user information.
The information included customers’ names, dates of birth, phone numbers and email addresses, as well as some driver’s license and passport numbers.
According to the Singapore-based company, no passwords or bank account details were stolen.
It is not yet known whether the attack was carried out by any state-sponsored or criminal organization, but Bayer Rosmarin said that no ransom was demanded.
“It is too early to rule out any possibility,” she noted, adding that police and the Australian government were investigating.
“We don’t yet know who these attackers are and what they want to do with this information,” she added.
The Australian Competition and Consumer Commission has warned potentially affected residents – which is almost half of the country’s population – that they could be at risk of identity theft.
Optus customers should take immediate steps to protect all their accounts, especially bank and financial accounts. You should also monitor your accounts for unusual activity and stay alert for scammers trying to contact you,” the regulator warned.