Department of Home Affairs secretary Stephanie Foster said she had used the messaging app Signal and in some cases, set her texts to disappear after a period of time.
"I use messaging apps, Signal included, for purposes that one might typically use a phone call for: to set up a meeting or ask if someone's free," she told Senate estimates on Thursday.
"Should I have a message that needs to be retained, then I absolutely know what my obligations are and I know how to retain it."
Greens senator David Shoebridge grilled the secretary over the app in reference to a "notorious" incident in the US, where a journalist was inadvertently added to a Signal group chat in which national security leaders were discussing American attacks on Houthi rebel sites in Yemen.
The chat included precise details about weapons, targets and the timing of bombings, alongside the officials' emoji-filled reactions.
Messages had been set to disappear after either one or four weeks, which raised questions over whether US laws had been violated as text messages about official acts are deemed records that should be preserved.
The Australian home affairs department has risk-assessed and accredited Signal in accordance with a system security framework, and has instituted particular protections.
Public servants must have a work account associated with the app and Signal can only be installed on their work devices.
There is no prohibition on disappearing messages, but employees have to be conscious of their record-keeping and privacy obligations, department officials assured.
