The Government Communications Security Bureau's (GSCB) fears over 5G are not isolated.
The intelligence agency recently declined a request from telco Spark to partner with Huawei in building its 5G network.
Now internet security company Symantec is warning that 5G will make us more vulnerable to cyber attacks.
Chief technology officer Nick Saviddes says the extra connectivity the new technology provides is a risk.
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The peak data rate of 5G networks is 10 Gbps, compared to 4G's 1 Gbps. Symantec warns the shift to 5F will "catalyse new operational models, new architectures, and consequently new vulnerabilities".
"As more 5G devices enter the market, they'll connect directly to the 5G network rather than via a Wi-Fi router, making the devices more vulnerable to direct attack."
Mr Savvides says attackers will also look to exploit artificial intelligence and automate their efforts, as attacks get more sophisticated.
"They can attack organisations and industrialise their efforts… and attack more organisations at the same time."
That includes attacking critical infrastructure - hence the GCSB's concern over Huawei, which has close links to the Chinese government. Huawei has denied its technology is used for espionage.
"An increasingly common target of attackers is the software supply chain, with attackers implanting malware into otherwise legitimate software packages," Symantec warns. "We could also see legitimate attempts to infect the hardware supply chain in the future."
'Social engineering attacks' on the rise
Symantec also warns 'deepfakes' will become a growing threat over the next 12 months too. That's where your face is put on another person's body - so far, mostly for porn. Hollywood celebrity Scarlett Johansson, whose face is reportedly popular amongst deepfake porn pranksters, recently said it was a "lost cause" trying to stop it.
"AI could leverage deepfakes to make social engineering attacks even more sophisticated," Symantec warned.
The best defence
But before you throw your phone in the trash, there's one key thing you can do to protect yourself.
"Worry about your identity - don't use the same password across multiple sites," says Mr Savvides. "If possible, turn on two-factor authentication."
Symantec expects further regulation along the lines of the European Union's General Data Protection Regulation to come into place to limit the possible damage.