Register now for FREE unlimited access to Reuters.com RegisterA woman uses her mobile phone as she walks past in front of an Optus shop in Sydney, Australia, February 8, 2018.
Register now for FREE unlimited access to Reuters.com RegisterOptus said it immediately shut down the attack after discovering it, and that payment details and account passwords had not been compromised.
The company's services, including mobile and home internet, are not affected, and messages and voice calls have not been compromised, it said.
"Optus services remain safe to use and operate as per normal," the company said in a statement, adding that it has notified the Australian Federal police and other key regulators regarding the breach.
Register now for FREE unlimited access to Reuters.com RegisterReporting by Tejaswi Marthi in Bengaluru; Editing by Devika SyamnathOur Standards: The Thomson Reuters Trust Principles.