Spark is warning of a security vulnerability which could compromise the devices and Wi-Fi networks of all its customers.
The fault - known as the KRACK vulnerability - was discovered by an overseas security researcher and could potentially allow a hacker to eavesdrop on Wi-Fi traffic.
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The hacker would have to be within a given Wi-Fi network's range and would only be able to look at traffic that hadn't been encrypted, Spark says.
The telecommunications company says the fault was discovered overnight, but it isn't aware of anyone affected by it yet.
A number of device manufacturers are now in the process of developing patches that would update software in response to the breach. Google, Microsoft and Apple have already issued statements on the vulnerability, and are well on the way to developing fixes.
The devices that require patches are Wi-Fi access points, such as modems, and other devices that connect to networks - including phones, tablets, PCs and laptops.
Spark says its Wi-Fi phone box network is still operational, but advised customers to take care.
They say they will keep customers abreast of any new details on the security breach or recommended actions as they come to light.