Australian telecommunications company Optus says that 2.1 million of its customers had numbers associated with their identification documents compromised in a recent data breach.
On September 22, the wireless carrier announced it had fallen victim to a cyberattack that resulted in the potential compromise of the personally identifiable information of some of its customers, without providing specifics on the number of impacted individuals.
Days after the attack was identified and addressed, a threat actor posted 10,000 Optus customer records on the dark web, threatening to make more information public unless the wireless carrier paid a $1 million ransom in cryptocurrency.
During the data breach, the attackers accessed user data such as names, dates of birth, email and home addresses, phone numbers, and personal identification document numbers.
The incident appears to have impacted the data of all of Optus’ 9.8 million customers, but the wireless carrier says that only the records of 1.2 million customers included a valid personal ID number.
For 900,000 additional customers, the compromised data contained numbers associated with expired IDs, Optus CEO Kelly Bayer Rosmarin said in a video posted on the company’s website.
She also noted that Optus has reached out to all the customers who had valid IDs exposed to inform them that personal data such as driver’s license numbers and card numbers was exposed. A total of 14,900 valid Medicare ID numbers were also compromised in the attack.
Bayer Rosmarin also said that Optus has launched a separate investigation into the incident and that international professional services firm Deloitte has been appointed to lead that operation.
“As part of the review, Deloitte will undertake a forensic assessment of the cyberattack and the circumstances surrounding it,” Optus said on Monday.
While the wireless carrier has not provided specific details on how the cyberattack occurred, it appears that the company might have inadvertently exposed internal resources to the internet, providing the attackers with an easy way in.
Australian officials have already pointed out that the incident will likely lead to tougher data protection legislation, meant to hold companies accountable for poorly protecting their customers’ information.