Debate about census 'made it a target'

All the talk about the security of the census meant the national survey became a big target, Malcolm Turnbull's cyber-security advisor says.

Alastair MacGibbon has been asked to review how denial-of-service attacks left the Australia Bureau of Statistics website in meltdown on Tuesday night.

"There was a lot of conjecture around the security and the preparation around this site, so it had a big birthmark on it that was shaped like a target," Mr MacGibbon told Sky News on Thursday.