, Medion Mobile and Optus have been issued formal warnings after the Australian Communications and Media Authority (ACMA) found they failed to adequately verify people's identities prior to transferring their mobile phone numbers from other telcos.
The ACMA found that in mid-2020, Telstra breached identity verification rules on at least 52 occasions, Medion Mobile on 53 occasions, and Optus on one occasion.
ACMA Chair Nerida O'Loughlin said that under new rules introduced in early 2020, telcos must have more rigorous customer verification processes in place, such as multifactor or in-person identification.
"Historically it has been too easy to transfer phone numbers from one telco to another. All a scammer needed to hijack a mobile number and access personal information like bank details was a name, address and date of birth," Ms O'Loughlin said.
"These new rules help prevent scammers from taking control of people's identities to commit serious financial crimes.
"We are cracking down on telcos that don't follow the rules and leave customers vulnerable to identity theft."
On average, victims lose more than $10,000 through identity theft from mobile number fraud and can be left struggling to regain control of their identities for long periods of time.
Since the new rules came into effect, reports of fraud have dropped dramatically.
"Some telcos are finding that fraudulent porting has stopped completely, and others report a drop of more than 90 per cent.
"It is important that telcos remain vigilant about protecting their customers through these verification processes," Ms O'Loughlin said.
The ACMA is actively monitoring industry compliance as part of its program to combat phone scams. Telcos that breach the rules could face civil penalties of up to $250,000.
