Telecommunications company Optus has suffered a massive cyberhack, potentially compromising the personal information of millions of Australians.
Reports suggest up to 2.8 million Australians have been implicated in the cybersecurity breach, which could have leaked information such as passport and licence numbers, email and home addresses, dates of birth and telephone numbers.
Payment details and Optus account passwords were not compromised.
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The breach implicates both past and present customers of Optus.
In a statement Optus said it "immediately shut down" the attack once it was aware of the breach and the Australian Federal Police have been notified.
"We are devastated to discover that we have been subject to a cyberattack that has resulted in the disclosure of our customers' personal information to someone who shouldn't see it," said Kelly Bayer Rosmarin, Optus CEO.
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"As soon as we knew, we took action to block the attack and began an immediate investigation.
"While not everyone maybe affected and our investigation is not yet complete, we want all of our customers to be aware of what has happened as soon as possible so that they can increase their vigilance.
"We are very sorry and understand customers will be concerned. Please be assured that we are working hard, and engaging with all the relevant authorities and organisations, to help safeguard our customers as much as possible."
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Rosmarin said the telco is not yet aware of any customers having suffered harm as a result of the breach.
"Optus has also notified key financial institutions about this matter," she said.
"While we are not aware of customers having suffered any harm, we encourage customers to have heightened awareness across their accounts, including looking out for unusual or fraudulent activity and any notifications which seem odd or suspicious."
Current services such as mobile and home internet are not affected, and the messages and voice calls of customers have not been compromised.
Optus says services remain safe to use and are operating as normal.
For customers who have specific concerns, they can contact Optus via the My Optus App (which remains the safest way to interact with Optus) or by calling 133 937. Optus will not be sending links in any emails or SMS messages.