Telstra and TPG are on guard against criminals looking to steal phone numbers from victims of the Optus data breach.

SIM-jacking, as the progress is called, sees criminals use various pieces of personal information in order to convince a telco to switch a victim’s phone number to a different device. This allows the criminal to commit deeper levels of identity fraud.

To counter this, Optus has locked SIM cards temporarily, but this is a temporary measure. Those with nefarious motives can simply wait it out until Optus unlocks the card.

SIM-jacking scams cost victims on average $28,000, according to the Australian Communications and Media Authority.

TPG, who owns the Vodafone phone in Australia, claims its lead in pre-port verification has meant “almost a complete halt to fraudulent port-in since July 2019.

“That means, fraudsters have not been able to take control of the services of non-Vodafone customers by moving their number to Vodafone.

“Since 2018, we have seen a reduction of more than 83 per cent in SIM-swap fraud due to the actions we have taken.

“We implemented a simple verification process to verify the authorisation of a port-in or a SIM-swap and championed industry-wide use of this process.

This approach has since been made a regulation in two separate Service Provider Determinations that deal with porting and more broadly with customer authorisation for high-risk transactions, such as SIM swaps and is now the industry norm.”

A Telstra spokesperson said: “Cybersecurity and protecting our customers’ data is key in everything we do.

“We monitor our network 24/7 and will continue to be on alert as we continue to reinforce our security using a range of technologies and security controls, to help minimise the likelihood and impact of unauthorised access to our networks and systems.”

Roughly 9.8 million former and current Optus customers had personal details compromised, including drivers’ licences, passports, Medicare cards, addresses and phone numbers.