The Department of Internal Affairs says it is not dismissing a threat to its website, which went down last week.
The department says its website is functioning again and it has not found any evidence to suggest hackers caused the failure.
The site went down last Tuesday and was restored by Friday night.
An internet group known as Anonymous posted a video on YouTube in February warning there would be an attack on the Internal Affairs website at 11am on Tuesday.
The group says the warning is aimed at forcing the department to remove internet filtering.
Anonymous was behind an attack that crippled Visa and Mastercard websites after the companies blocked donations to whistle-blowing website WikiLeaks.
A department spokesperson, Tony Wallace, says it is not dismissing the threat and is prepared if it happens.