Home Affairs' website and online portals were targeted in a distributed denial-of-service attack preventing user access late last week.
"The Department of Home Affairs is aware of a DDoS attack on the department’s website that briefly prevented access to both the website and online portals," it said in a statement.
"No departmental holdings, including personal or sensitive information, were accessed by the threat actor.
"An investigation into the circumstances surrounding the incident is under way, but initial assessments indicate that the DDoS attack was solely designed to prevent access to our websites."
The incident started at about 10pm AEDT on Thursday night; public access to the site was restored at around 3.10am the following day.
SBS News reported that the website of the Administrative Appeals Tribunal (AAT) was hit by the same person or group.
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